ale*_*lex 745 javascript arrays
在PHP中,你可以做...
range(1, 3); // Array(1, 2, 3)
range("A", "C"); // Array("A", "B", "C")
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也就是说,有一个函数可以通过传递上限和下限来获取一系列数字或字符.
是否内置了JavaScript本身的内容?如果没有,我将如何实施它?
Ben*_*Ben 1242
数字
[...Array(5).keys()];
=> [0, 1, 2, 3, 4]
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字符迭代
String.fromCharCode(...[...Array('D'.charCodeAt(0) - 'A'.charCodeAt(0) + 1).keys()].map(i => i + 'A'.charCodeAt(0)));
=> "ABCD"
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迭代
for (const x of Array(5).keys()) {
console.log(x, String.fromCharCode('A'.charCodeAt(0) + x));
}
=> 0,"A" 1,"B" 2,"C" 3,"D" 4,"E"
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作为功能
function range(size, startAt = 0) {
return [...Array(size).keys()].map(i => i + startAt);
}
function characterRange(startChar, endChar) {
return String.fromCharCode(...range(endChar.charCodeAt(0) -
startChar.charCodeAt(0), startChar.charCodeAt(0)))
}
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作为打字功能
function range(size:number, startAt:number = 0):ReadonlyArray<number> {
return [...Array(size).keys()].map(i => i + startAt);
}
function characterRange(startChar:string, endChar:string):ReadonlyArray<string> {
return String.fromCharCode(...range(endChar.charCodeAt(0) -
startChar.charCodeAt(0), startChar.charCodeAt(0)))
}
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lodash.js _.range()功能
_.range(10);
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
_.range(1, 11);
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
_.range(0, 30, 5);
=> [0, 5, 10, 15, 20, 25]
_.range(0, -10, -1);
=> [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
String.fromCharCode(..._.range('A'.charCodeAt(0), 'D'.charCodeAt(0) + 1));
=> "ABCD"
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没有库的旧非es6浏览器:
Array.apply(null, Array(5)).map(function (_, i) {return i;});
=> [0, 1, 2, 3, 4]
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console.log([...Array(5).keys()]);Run Code Online (Sandbox Code Playgroud)
谢谢.
(ES6归功于nils petersohn和其他评论者)
Cap*_*apK 297
对于数字,你可以使用ES6 Array.from(),这些日子除了IE以外的所有东西都可以使用:
更短的版本:
Array.from({length: 20}, (x,i) => i);
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更长的版本:
Array.from(new Array(20), (x,i) => i)
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它创建一个从0到19(包括0和19)的数组.这可以进一步缩短为以下形式之一:
Array.from(Array(20).keys())
// or
[...Array(20).keys()]
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也可以指定下限和上限,例如:
Array.from(new Array(20), (x,i) => i + *lowerBound*)
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一篇文章更详细地描述了这一点:http://www.2ality.com/2014/05/es6-array-methods.html
Kut*_*yel 109
我最喜欢的表格(ES2015)
Array(10).fill(1).map((x, y) => x + y)
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如果你需要一个带step参数的函数:
const range = (start, stop, step = 1) =>
Array(Math.ceil((stop - start) / step)).fill(start).map((x, y) => x + y * step)
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jfl*_*net 98
这是我的2美分:
function range(start, count) {
return Array.apply(0, Array(count))
.map((element, index) => index + start);
}
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ale*_*lex 70
它适用于字符和数字,可选步骤前进或后退.
var range = function(start, end, step) {
var range = [];
var typeofStart = typeof start;
var typeofEnd = typeof end;
if (step === 0) {
throw TypeError("Step cannot be zero.");
}
if (typeofStart == "undefined" || typeofEnd == "undefined") {
throw TypeError("Must pass start and end arguments.");
} else if (typeofStart != typeofEnd) {
throw TypeError("Start and end arguments must be of same type.");
}
typeof step == "undefined" && (step = 1);
if (end < start) {
step = -step;
}
if (typeofStart == "number") {
while (step > 0 ? end >= start : end <= start) {
range.push(start);
start += step;
}
} else if (typeofStart == "string") {
if (start.length != 1 || end.length != 1) {
throw TypeError("Only strings with one character are supported.");
}
start = start.charCodeAt(0);
end = end.charCodeAt(0);
while (step > 0 ? end >= start : end <= start) {
range.push(String.fromCharCode(start));
start += step;
}
} else {
throw TypeError("Only string and number types are supported");
}
return range;
}
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如果扩展本机类型是您的事情,那么将其分配给Array.range.
var range = function(start, end, step) {
var range = [];
var typeofStart = typeof start;
var typeofEnd = typeof end;
if (step === 0) {
throw TypeError("Step cannot be zero.");
}
if (typeofStart == "undefined" || typeofEnd == "undefined") {
throw TypeError("Must pass start and end arguments.");
} else if (typeofStart != typeofEnd) {
throw TypeError("Start and end arguments must be of same type.");
}
typeof step == "undefined" && (step = 1);
if (end < start) {
step = -step;
}
if (typeofStart == "number") {
while (step > 0 ? end >= start : end <= start) {
range.push(start);
start += step;
}
} else if (typeofStart == "string") {
if (start.length != 1 || end.length != 1) {
throw TypeError("Only strings with one character are supported.");
}
start = start.charCodeAt(0);
end = end.charCodeAt(0);
while (step > 0 ? end >= start : end <= start) {
range.push(String.fromCharCode(start));
start += step;
}
} else {
throw TypeError("Only string and number types are supported");
}
return range;
}
console.log(range("A", "Z", 1));
console.log(range("Z", "A", 1));
console.log(range("A", "Z", 3));
console.log(range(0, 25, 1));
console.log(range(0, 25, 5));
console.log(range(20, 5, 5));Run Code Online (Sandbox Code Playgroud)
Rem*_*emi 47
简单范围功能:
function range(start, stop, step) {
var a = [start], b = start;
while (b < stop) {
a.push(b += step || 1);
}
return a;
}
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ken*_*bec 35
Array.range= function(a, b, step){
var A= [];
if(typeof a== 'number'){
A[0]= a;
step= step || 1;
while(a+step<= b){
A[A.length]= a+= step;
}
}
else{
var s= 'abcdefghijklmnopqrstuvwxyz';
if(a=== a.toUpperCase()){
b=b.toUpperCase();
s= s.toUpperCase();
}
s= s.substring(s.indexOf(a), s.indexOf(b)+ 1);
A= s.split('');
}
return A;
}
Array.range(0,10);
// [0,1,2,3,4,5,6,7,8,9,10]
Array.range(-100,100,20);
// [-100,-80,-60,-40,-20,0,20,40,60,80,100]
Array.range('A','F');
// ['A','B','C','D','E','F')
Array.range('m','r');
// ['m','n','o','p','q','r']
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Ali*_*eza 35
好的,在JavaScript中我们没有range()像PHP这样的函数,所以我们需要创建一个非常容易的函数,我为你编写了几个单行函数,并将它们分别用于Numbers和Alphabets,如下所示:
对于数字:
function numberRange (start, end) {
return new Array(end - start).fill().map((d, i) => i + start);
}
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并称之为:
numberRange(5, 10); //[5, 6, 7, 8, 9]
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对于字母:
function alphabetRange (start, end) {
return new Array(end.charCodeAt(0) - start.charCodeAt(0)).fill().map((d, i) => String.fromCharCode(i + start.charCodeAt(0)));
}
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并称之为:
alphabetRange('c', 'h'); //["c", "d", "e", "f", "g"]
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nki*_*tku 27
[...Array(N)].map((_, i) => from + i * step);
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示例和其他替代方案
[...Array(10)].map((_, i) => 4 + i * 2);
//=> [4, 6, 8, 10, 12, 14, 16, 18, 20, 22]
Array.from(Array(10)).map((_, i) => 4 + i * 2);
//=> [4, 6, 8, 10, 12, 14, 16, 18, 20, 22]
Array.from(Array(10).keys()).map(i => 4 + i * 2);
//=> [4, 6, 8, 10, 12, 14, 16, 18, 20, 22]
[...Array(10).keys()].map(i => 4 + i * -2);
//=> [4, 2, 0, -2, -4, -6, -8, -10, -12, -14]
Array(10).fill(0).map((_, i) => 4 + i * 2);
//=> [4, 6, 8, 10, 12, 14, 16, 18, 20, 22]
Array(10).fill().map((_, i) => 4 + i * -2);
//=> [4, 2, 0, -2, -4, -6, -8, -10, -12, -14]
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范围函数
const range = (from, to, step) =>
[...Array(Math.floor((to - from) / step) + 1)].map((_, i) => from + i * step);
range(0, 9, 2);
//=> [0, 2, 4, 6, 8]
// can also assign range function as static method in Array class (but not recommended )
Array.range = (from, to, step) =>
[...Array(Math.floor((to - from) / step) + 1)].map((_, i) => from + i * step);
Array.range(2, 10, 2);
//=> [2, 4, 6, 8, 10]
Array.range(0, 10, 1);
//=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Array.range(2, 10, -1);
//=> []
Array.range(3, 0, -1);
//=> [3, 2, 1, 0]
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作为迭代器
class Range {
constructor(total = 0, step = 1, from = 0) {
this[Symbol.iterator] = function* () {
for (let i = 0; i < total; yield from + i++ * step) {}
};
}
}
[...new Range(5)]; // Five Elements
//=> [0, 1, 2, 3, 4]
[...new Range(5, 2)]; // Five Elements With Step 2
//=> [0, 2, 4, 6, 8]
[...new Range(5, -2, 10)]; // Five Elements With Step -2 From 10
//=>[10, 8, 6, 4, 2]
[...new Range(5, -2, -10)]; // Five Elements With Step -2 From -10
//=> [-10, -12, -14, -16, -18]
// Also works with for..of loop
for (i of new Range(5, -2, 10)) console.log(i);
// 10 8 6 4 2
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仅作为发电机
const Range = function* (total = 0, step = 1, from = 0) {
for (let i = 0; i < total; yield from + i++ * step) {}
};
Array.from(Range(5, -2, -10));
//=> [-10, -12, -14, -16, -18]
[...Range(5, -2, -10)]; // Five Elements With Step -2 From -10
//=> [-10, -12, -14, -16, -18]
// Also works with for..of loop
for (i of Range(5, -2, 10)) console.log(i);
// 10 8 6 4 2
// Lazy loaded way
const number0toInf = Range(Infinity);
number0toInf.next().value;
//=> 0
number0toInf.next().value;
//=> 1
// ...
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class Range2 {
constructor(to = 0, step = 1, from = 0) {
this[Symbol.iterator] = function* () {
let i = 0,
length = Math.floor((to - from) / step) + 1;
while (i < length) yield from + i++ * step;
};
}
}
[...new Range2(5)]; // First 5 Whole Numbers
//=> [0, 1, 2, 3, 4, 5]
[...new Range2(5, 2)]; // From 0 to 5 with step 2
//=> [0, 2, 4]
[...new Range2(5, -2, 10)]; // From 10 to 5 with step -2
//=> [10, 8, 6]
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使用发电机
const Range2 = function* (to = 0, step = 1, from = 0) {
let i = 0,
length = Math.floor((to - from) / step) + 1;
while (i < length) yield from + i++ * step;
};
[...Range2(5, -2, 10)]; // From 10 to 5 with step -2
//=> [10, 8, 6]
let even4to10 = Range2(10, 2, 4);
even4to10.next().value;
//=> 4
even4to10.next().value;
//=> 6
even4to10.next().value;
//=> 8
even4to10.next().value;
//=> 10
even4to10.next().value;
//=> undefined
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class _Array<T> extends Array<T> {
static range(from: number, to: number, step: number): number[] {
return Array.from(Array(Math.floor((to - from) / step) + 1)).map(
(v, k) => from + k * step
);
}
}
_Array.range(0, 9, 1);
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class _Array<T> extends Array<T> {
static range(from: number, to: number, step: number): number[] {
return Array.from(Array(Math.floor((to - from) / step) + 1)).map(
(v, k) => from + k * step
);
}
}
_Array.range(0, 9, 1);
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const charList = (p: string, q: string, d = 1) => {
const a = p.charCodeAt(0),
z = q.charCodeAt(0);
return [...Array(Math.floor((z - a) / d) + 1)].map((_, i) =>
String.fromCharCode(a + i * d)
);
};
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alo*_*ica 26
如果在 Visual Studio Code 上遇到以下错误:

类型“IterableIterator”不是数组类型或字符串类型。使用编译器选项“--downlevelIteration”允许迭代器进行迭代。
代替
[...Array(3).keys()]
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你可以信赖
Array.from(Array(3).keys())
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aze*_*ati 23
方便的功能来完成这个技巧,运行下面的代码片段
function range(start, end, step, offset) {
var len = (Math.abs(end - start) + ((offset || 0) * 2)) / (step || 1) + 1;
var direction = start < end ? 1 : -1;
var startingPoint = start - (direction * (offset || 0));
var stepSize = direction * (step || 1);
return Array(len).fill(0).map(function(_, index) {
return startingPoint + (stepSize * index);
});
}
console.log('range(1, 5)=> ' + range(1, 5));
console.log('range(5, 1)=> ' + range(5, 1));
console.log('range(5, 5)=> ' + range(5, 5));
console.log('range(-5, 5)=> ' + range(-5, 5));
console.log('range(-10, 5, 5)=> ' + range(-10, 5, 5));
console.log('range(1, 5, 1, 2)=> ' + range(1, 5, 1, 2));Run Code Online (Sandbox Code Playgroud)
这是如何使用它
范围(开始,结束,步骤= 1,偏移= 0);
range(5,10) // [5, 6, 7, 8, 9, 10]range(10,5) // [10, 9, 8, 7, 6, 5]range(10,2,2) // [10, 8, 6, 4, 2]range(5,10,0,-1) // [6, 7, 8, 9] not 5,10 themselvesrange(5,10,0,1) // [4, 5, 6, 7, 8, 9, 10, 11]range(5,10,0,-2) // [7, 8]range(10,0,2,2) // [12, 10, 8, 6, 4, 2, 0, -2]希望你觉得它有用.
这是它的工作原理.
基本上我首先计算结果数组的长度,并为该长度创建一个零填充数组,然后用所需的值填充它
(step || 1)=>和其他类似的.这意味着使用的值step,并且如果它未提供使用1,而不是(Math.abs(end - start) + ((offset || 0) * 2)) / (step || 1) + 1)使其更简单(两个方向/步骤的差异*偏移)new Array(length).fill(0); [0,0,0,..]我们想要的长度数组.我们映射它并使用我们需要的值返回一个新数组Array.map(function() {})var direction = start < end ? 1 : 0;显然,如果start不小于end我们需要向后移动.我的意思是从0到5,反之亦然startingPoint+ stepSize*index将为我们提供所需的价值Art*_*sun 22
var range = (l,r) => new Array(r - l).fill().map((_,k) => k + l);
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c.P*_*.u1 18
使用Harmony 传播操作符和箭头函数:
var range = (start, end) => [...Array(end - start + 1)].map((_, i) => start + i);
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例:
range(10, 15);
[ 10, 11, 12, 13, 14, 15 ]
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Mik*_*scu 16
标准Javascript没有内置函数来生成范围.一些javascript框架添加了对这些功能的支持,或者正如其他人指出的那样,你可以随时使用自己的功能.
如果您想仔细检查,最终资源是ECMA-262标准.
Jus*_*tin 14
对一些不同的范围函数进行了一些研究. 检查jsperf比较执行这些功能的不同方法.当然不是一个完美或详尽的清单,但应该帮助:)
获胜者是......
function range(lowEnd,highEnd){
var arr = [],
c = highEnd - lowEnd + 1;
while ( c-- ) {
arr[c] = highEnd--
}
return arr;
}
range(0,31);
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从技术上讲,它不是firefox上最快的,但是Chrome上的疯狂速度差异(imho)弥补了它.
同样有趣的观察是这些数组函数的速度比firefox快多少.Chrome的速度至少快4到5倍.
Pao*_*tti 13
你可以使用lodash或Undescore.js range:
var range = require('lodash/range')
range(10)
// -> [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
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或者,如果您只需要一个连续的整数范围,您可以执行以下操作:
Array.apply(undefined, { length: 10 }).map(Number.call, Number)
// -> [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
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在ES6中range可以使用生成器实现:
function* range(start=0, end=null, step=1) {
if (end == null) {
end = start;
start = 0;
}
for (let i=start; i < end; i+=step) {
yield i;
}
}
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这种实现在迭代大型序列时可以节省内存,因为它不必将所有值都实现为数组:
for (let i of range(1, oneZillion)) {
console.log(i);
}
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LKB*_*LKB 13
(from, to) => [...Array(to - from)].map((_,i)=> i + from)
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DIN*_*LIT 13
如果只想使用范围来重复过程 n 次,您可以简单地使用此代码
[...Array(10)].map((item, index) => (
console.log("item:", index)
))
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Her*_* Qu 12
使用ES6发生器的另一个版本(参见伟大的Paolo Moretti回答ES6发生器):
const RANGE = (a,b) => Array.from((function*(x,y){
while (x <= y) yield x++;
})(a,b));
console.log(RANGE(3,7)); // [ 3, 4, 5, 6, 7 ]
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或者,如果我们只需要迭代,那么:
const RANGE_ITER = (a,b) => (function*(x,y){
while (x <= y) yield x++;
})(a,b);
for (let n of RANGE_ITER(3,7)){
console.log(n);
}
// 3
// 4
// 5
// 6
// 7
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小智 12
我个人最喜欢的:
const range = (start, end) => new Array(end-start+1).fill().map((el, ind) => ind + start);
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Ric*_*ock 10
一个有趣的挑战是编写最短的函数来做到这一点.救援的递归!
function r(a,b){return a>b?[]:[a].concat(r(++a,b))}
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在大范围内趋于缓慢,但幸运的是量子计算机即将到来.
一个额外的好处是它是混淆的.因为我们都知道将我们的代码隐藏起来是多么重要.
要真正彻底地混淆函数,请执行以下操作:
function r(a,b){return (a<b?[a,b].concat(r(++a,--b)):a>b?[]:[a]).sort(function(a,b){return a-b})}
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我会编码这样的代码:
function range(start, end) {
return Array(end-start).join(0).split(0).map(function(val, id) {return id+start});
}
range(-4,2);
// [-4,-3,-2,-1,0,1]
range(3,9);
// [3,4,5,6,7,8]
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它的行为类似于Python范围:
>>> range(-4,2)
[-4, -3, -2, -1, 0, 1]
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这个也可以反向工作。
const range = ( a , b ) => Array.from( new Array( b > a ? b - a : a - b ), ( x, i ) => b > a ? i + a : a - i );
range( -3, 2 ); // [ -3, -2, -1, 0, 1 ]
range( 1, -4 ); // [ 1, 0, -1, -2, -3 ]
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可以如下创建大量使用ES6的相当简约的实现,特别注意Array.from()静态方法:
const getRange = (start, stop) => Array.from(
new Array((stop - start) + 1),
(_, i) => i + start
);
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尚未实施!
使用新Number.range 提案(阶段 1):
[...Number.range(1, 10)]
//=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
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小智 7
虽然这不是来自PHP,而是range来自Python的模仿.
function range(start, end) {
var total = [];
if (!end) {
end = start;
start = 0;
}
for (var i = start; i < end; i += 1) {
total.push(i);
}
return total;
}
console.log(range(10)); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
console.log(range(0, 10)); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
console.log(range(5, 10)); // [5, 6, 7, 8, 9]
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range(start,end,step):使用ES6迭代器您只要求一个上限和下限。在这里,我们也创建了一个步骤。
您可以轻松地创建range()可用作迭代器的生成器函数。这意味着您不必预先生成整个数组。
function * range ( start, end, step = 1 ) {
let state = start;
while ( state < end ) {
yield state;
state += step;
}
return;
};
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现在,您可能需要创建一些东西,以便从迭代器中预生成数组并返回一个列表。这对于接受数组的函数很有用。为此,我们可以使用Array.from()
const generate_array = (start,end,step) =>
Array.from( range(start,end,step) );
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现在,您可以轻松生成静态数组,
const array1 = generate_array(1,10,2);
const array1 = generate_array(1,7);
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但是,当某些东西需要迭代器(或为您提供使用迭代器的选项)时,您也可以轻松创建一个迭代器。
for ( const i of range(1, Number.MAX_SAFE_INTEGER, 7) ) {
console.log(i)
}
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R.range和Lodash一样都有自己的您可以使用以下单行代码来使事情简短而简单
var start = 4;
var end = 20;
console.log(Array(end - start + 1).fill(start).map((x, y) => x + y));Run Code Online (Sandbox Code Playgroud)
用这个。它创建一个具有给定数量值(未定义)的数组,在下面的示例中有 100 个索引,但它不相关,因为在这里您只需要键。它在数组中使用 100 + 1,因为数组总是基于 0 索引。因此,如果要生成 100 个值,则索引从 0 开始;因此最后一个值总是 99 而不是 100。
range(2, 100);
function range(start, end) {
console.log([...Array(end + 1).keys()].filter(value => end >= value && start <= value ));
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使用Harmony生成器,除IE11以外的所有浏览器都支持:
var take = function (amount, generator) {
var a = [];
try {
while (amount) {
a.push(generator.next());
amount -= 1;
}
} catch (e) {}
return a;
};
var takeAll = function (gen) {
var a = [],
x;
try {
do {
x = a.push(gen.next());
} while (x);
} catch (e) {}
return a;
};
var range = (function (d) {
var unlimited = (typeof d.to === "undefined");
if (typeof d.from === "undefined") {
d.from = 0;
}
if (typeof d.step === "undefined") {
if (unlimited) {
d.step = 1;
}
} else {
if (typeof d.from !== "string") {
if (d.from < d.to) {
d.step = 1;
} else {
d.step = -1;
}
} else {
if (d.from.charCodeAt(0) < d.to.charCodeAt(0)) {
d.step = 1;
} else {
d.step = -1;
}
}
}
if (typeof d.from === "string") {
for (let i = d.from.charCodeAt(0); (d.step > 0) ? (unlimited ? true : i <= d.to.charCodeAt(0)) : (i >= d.to.charCodeAt(0)); i += d.step) {
yield String.fromCharCode(i);
}
} else {
for (let i = d.from; (d.step > 0) ? (unlimited ? true : i <= d.to) : (i >= d.to); i += d.step) {
yield i;
}
}
});
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采取
例1.
take 只需要尽可能多的钱
take(10, range( {from: 100, step: 5, to: 120} ) )
回报
[100, 105, 110, 115, 120]
例2.
to 不是必要的
take(10, range( {from: 100, step: 5} ) )
回报
[100, 105, 110, 115, 120, 125, 130, 135, 140, 145]
takeAll
例3.
from 不是必要的
takeAll( range( {to: 5} ) )
回报
[0, 1, 2, 3, 4, 5]
例4.
takeAll( range( {to: 500, step: 100} ) )
回报
[0, 100, 200, 300, 400, 500]
例5.
takeAll( range( {from: 'z', to: 'a'} ) )
回报
["z", "y", "x", "w", "v", "u", "t", "s", "r", "q", "p", "o", "n", "m", "l", "k", "j", "i", "h", "g", "f", "e", "d", "c", "b", "a"]
至于为给定范围生成数值数组,我使用:
function range(start, stop)
{
var array = [];
var length = stop - start;
for (var i = 0; i <= length; i++) {
array[i] = start;
start++;
}
return array;
}
console.log(range(1, 7)); // [1,2,3,4,5,6,7]
console.log(range(5, 10)); // [5,6,7,8,9,10]
console.log(range(-2, 3)); // [-2,-1,0,1,2,3]
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显然,它不适用于字母数组.
d3 还有一个内置的 range 函数。见https://github.com/mbostock/d3/wiki/Arrays#d3_range:
d3.range([start, ]stop[, step])
生成一个包含等差数列的数组,类似于 Python 内置范围。此方法通常用于迭代一系列数字或整数值,例如数组中的索引。与 Python 版本不同,参数不需要是整数,但如果由于浮点精度,结果更可预测。如果省略 step,则默认为 1。
例子:
d3.range(10)
// returns [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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我的 codegolfing 同事想出了这个(ES6),包括:
(s,f)=>[...Array(f-s+1)].map((e,i)=>i+s)
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不包括:
(s,f)=>[...Array(f-s)].map((e,i)=>i+s)
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这可能不是最好的方法。但是,如果您希望在一行代码中获得一系列数字。例如10-50
Array(40).fill(undefined).map((n, i) => i + 10)
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其中40是(结束-开始),而10是开始。这应该返回[10,11,...,50]
使用 range([start, ]stop[, step]) 签名完成 ES6 实现:
function range(start, stop, step=1){
if(!stop){stop=start;start=0;}
return Array.from(new Array(int((stop-start)/step)), (x,i) => start+ i*step)
}
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如果您想要自动负步进,请添加
if(stop<start)step=-Math.abs(step)
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或者更简约:
range=(b, e, step=1)=>{
if(!e){e=b;b=0}
return Array.from(new Array(int((e-b)/step)), (_,i) => b<e? b+i*step : b-i*step)
}
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如果您的范围很大,请查看 Paolo Moretti 的生成器方法
小智 5
...更多范围,使用发电机功能.
function range(s, e, str){
// create generator that handles numbers & strings.
function *gen(s, e, str){
while(s <= e){
yield (!str) ? s : str[s]
s++
}
}
if (typeof s === 'string' && !str)
str = 'abcdefghijklmnopqrstuvwxyz'
const from = (!str) ? s : str.indexOf(s)
const to = (!str) ? e : str.indexOf(e)
// use the generator and return.
return [...gen(from, to, str)]
}
// usage ...
console.log(range('l', 'w'))
//=> [ 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w' ]
console.log(range(7, 12))
//=> [ 7, 8, 9, 10, 11, 12 ]
// first 'o' to first 't' of passed in string.
console.log(range('o', 't', "ssshhhooooouuut!!!!"))
// => [ 'o', 'o', 'o', 'o', 'o', 'u', 'u', 'u', 't' ]
// only lowercase args allowed here, but ...
console.log(range('m', 'v').map(v=>v.toUpperCase()))
//=> [ 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V' ]
// => and decreasing range ...
console.log(range('m', 'v').map(v=>v.toUpperCase()).reverse())
// => ... and with a step
console.log(range('m', 'v')
.map(v=>v.toUpperCase())
.reverse()
.reduce((acc, c, i) => (i % 2) ? acc.concat(c) : acc, []))
// ... etc, etc.
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希望这很有用.
小智 5
ES6
使用 Array.from(此处为文档):
const range = (start, stop, step) => Array.from({ length: (stop - start) / step + 1}, (_, i) => start + (i * step));
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您还可以使用生成器来生成序列。\n不同之处在于序列中的每个值都是延迟加载的。扩展运算符和 for of 计算结果。\n星号使该函数成为生成器。
\nconst range = function*(from,to) { \xc2\xa0 \n for(let i = from; i <= to; i++) yield I; \xc2\xa0 \n}; \xc2\xa0 \n\n[...range(3,5)]// => [3, 4, 5]\nRun Code Online (Sandbox Code Playgroud)\n
Op 要求一个范围,比如range(3, 10),所以它可以是
[...[...Array(10-3).keys()].map(i => i+3)]
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回报
[3, 4, 5, 6, 7, 8, 9]
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