const instance = Symbol('instance');
class Parent {
number;
constructor() {
const Class = this.constructor;
if (!Class[instance]) Class[instance] = this;
return Class[instance];
}
set_number (number) {
this.number = number;
}
}
class Child extends Parent {
test () { }
}
class Child2 extends Parent {
test () { }
}
const child = new Child();
const parent = new Parent();
const child2 = new Child2();
child.set_number(1);
child.test();
child2.set_number(2);
child2.test(); // child2.test is not a function
parent.set_number(3);
console.log(child.number); // output : …我正在使用graphql-tag。我的文件就是这样的。
./操作.graphql
Query User {
...
}
./测试.ts
import { User } from './operation.graphql'; /// Module ''*.graphql'' has no exported member 'User'.
./index.d.ts
declare module '*.graphql' {
import { DocumentNode } from 'graphql';
const value:DocumentNode;
export default value;
}
应用程序运行良好，但我想防止该错误。
当我执行默认导入时效果很好，但正如您所见，我在命名导入时遇到错误。
如何声明这一点？谢谢。:)
我使用React 16.0。
我想有条件地返回一个元素，如下所示。
import React from 'react';
export default class App extends React.PureComponent {
render () {
return [
<div className="a"></div>,
{condition ? <div className="b"></div> : null},
{condition ? <div className="c"></div> : null}
];
}
}
有没有办法在 return 语句之外不需要任何额外的方法或条件语句来做到这一点？
感谢您的阅读。
interface Test {
a: string;
b: number;
c: number;
}
const test = {
a: 'a',
b: 1,
d: []
};
delete test.d;
const test2:Test = { ...test, c:1 };
=> Type '{ a: string; b: number; c: number; d: never[]; }' is not assignable to type 'Test'.
=> Object literal may only specify known properties, and 'd' does not exist in type 'Test'.
我通过删除运算符删除了d属性，但出现了类似的错误。
针对这种情况有办法吗？
import { createAction, handleActions } from 'redux-actions';
import { delay } from 'redux-saga';
import { all, put, takeEvery } from 'redux-saga/effects';
export const action_creators = {
get_action_of_set_number: createAction<{ number:number }>('set_number'),
get_action_of_set_number_async: createAction<{ number:number }>('set_number_async')
};
const state = {
number: 0
}
function* set_number_async(action: { payload: { number:number } }) {
yield delay(1000);
yield put(action_creators.get_action_of_set_number(action.payload));
}
export function* saga(action) {
yield all([takeEvery('set_number_async', set_number_async)]);
*** Error message : Argument of type '"set_number_async"' is not assignable
*** to parameter of type 'Channel<{ …我不知道如何填写句子"如果通过initial_value".我必须使用变量参数吗？它对我来说不太可读,所以我找到了其他方法.
请帮帮我..
int *func (int initial_value) {
int *number;
number = malloc(sizeof(int));
if ("if initial_value is passed") *number = initial_value;
else scanf("%d", &number);
return number;
}
有以下数据.
[
{"no":1, "name":"ELECTRONICS", "depth":0},
{"no":2, "name":"TELEVISIONS", "depth":1},
{"no":3, "name":"TUBE", "depth":2},
{"no":4, "name":"LCD", "depth":2},
{"no":5, "name":"PLASMA", "depth":2},
{"no":6, "name":"PORTABLE ELECTRONICS", "depth":1},
{"no":7, "name":"MP3 PLAYERS", "depth":2},
{"no":8, "name":"FLASH", "depth":3},
{"no":9, "name":"CD PLAYERS", "depth":2},
{"no":10, "name":"2 WAY RADIOS", "depth":2}
]
我想获得如下数据.
[
{
"no":1,
"name":"ELECTRONICS",
"depth":0,
"child_nodes":[
{
"no":2,
"name":"TELEVISIONS",
"depth":1
"child_nodes":[
{
"no":3,
"name":"TUBE",
"depth":2
},
...
]
},
{
"no":6,
"name":"PORTABLE ELECTRONICS",
"depth":1
"child_nodes":[ ... ]
}
]
}
]
我正在递归地尝试它,但它并不好.由于我使用的是babel,因此对javascript的新功能没有很大的限制.如果你有个好主意,请告诉我.谢谢!
我想知道它是否具有以下任何功能。我尝试了Google，但找不到。谢谢！
interface Numbers {
number: number;
number2: number;
number3: number;
}
const numbers:Numbers - { number3 } = {
number: 1,
number2: 2
};
typescript ×4
javascript ×3
arrays ×2
reactjs ×2
arguments ×1
c ×1
depth ×1
ecmascript-6 ×1
graphql ×1
graphql-tag ×1
module ×1
nested-sets ×1
redux ×1
redux-saga ×1
return ×1