javascript包含()不区分大小写

Question

假设我有一个过滤字符串数组,我需要循环并检查其他传入的字符串.

var filterstrings = ['firststring','secondstring','thridstring'];
var passedinstring = localStorage.getItem("passedinstring");

for (i = 0; i < filterstrings.lines.length; i++) {
    if (passedinstring.includes(filterstrings[i])) {
        alert("string detected");
    }
}

我如何确保在过滤时忽略区分大小写(最好是使用正则表达式),如果var passedinstring要使用FirsTsTriNg或者字符串fiRSTStrING？

Answer 1

ES6数组方法filter()可以简单的单行解决，使用includes()方法判断数组是否包含某个值，并结合toLowerCase()方法将其转换为小写。

var filterstrings = ['firststring','secondstring','thridstring'];
var passedinstring = localStorage.getItem("passedinstring");

// convert each string from filterstrings and passedinstring to lowercase
// to avoid case sensitive issue.
filteredStrings = filterstrings.filter((str) => str.toLowerCase().includes(passedinstring.toLowerCase())

Answer 2

您可以.includes使用.some返回boolean的方法进行切换。一旦找到匹配
它就会退出，这对于大型数组的性能非常有用：

.some(item => item.toLowerCase() == lookup.toLowerCase())

演示：

var arr = ['foo','bar','bar'];
var lookup = "bAr";

// case-sensetive
console.log( arr.includes(lookup) )

// case-insensetive without caring about the type
console.log( arr.some(x => x.toLowerCase() == lookup.toLowerCase()) ) 

或者使用唯一的名称定义您自己的数组原型方法：

// the name ("_includes") should be unique enough not to ever be overriten 
// by future language updates or 3rd-party scripts
Array.prototype._includes = function(target){ 
  return this.some(x => x.toLowerCase() == (target||'').toLowerCase()) 
}

console.log( 
  ['foo', 'bar', 'bar']._includes("bAr") 
)

Answer 3

您可以从一开始创建一个RegExpfilterstrings

var filterstrings = ['firststring','secondstring','thridstring'];
var regex = new RegExp( filterstrings.join( "|" ), "i");

那么test如果passedinstring那里

var isAvailable = regex.test( passedinstring ); 

Answer 4

你可以简单地转换passedinstring为小写。

var passedinstring = localStorage.getItem("passedinstring").toLowerCase();

Answer 5

将 filterstring 和 passinstring 转换为小写并进行比较

var filterstrings = ['firststring','secondstring','thridstring'];
var passedinstring = 
localStorage.getItem("passedinstring").toLowerCase();

for (i = 0; i < filterstrings.lines.length; i++) {
   if (passedinstring.includes(filterstrings[i].toLowerCase())) {
       alert("string detected");
   }
}

Answer 6

使用toLowerCase(). 比较时它全部string变成小写。

var product=productList.filter((x) => x.Name.toLowerCase().includes(("Active").toLowerCase()))

Answer 7

我的选择是比较 UPPER 与 UPPER 或 lower 与 lower 转换两侧（我经常在 SQL 中这样做）：

    var filterstrings = ['firststring','secondstring','thirDstrIng'];
    var passedinstring =  'ThIrDsTrInG3';
    
    //used for of just to make it more readable
    for (filterstring of filterstrings) {
        if (passedinstring.toUpperCase().includes(filterstring.toUpperCase())) {
            alert("string detected");
        }
    
    }

提示string detected