javascript include() 不区分大小写

Question

我有一个字符串数组，我需要循环并检查另一个传入的字符串。

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");
    }
}

如果var passedinstring 包含FirsTsTriNg 或fiRSTStrING 之类的字符串，我如何确保在过滤时忽略大小写（最好使用正则表达式）？

Answer 1

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

filterstrings.filter(item => item.name.toLowerCase().includes(passedinstring.toLowerCase()))

Answer 2

你可以试试这个。

var fruits = ["Banana", "Orange", "Apple", "Mango"];
string = fruits.join(' ').toUpperCase();
// Output"BANANA ORANGE APPLE MANGO"

Answer 3

您可以使用返回布尔值的.some 方法切换.includes。
它会在找到匹配项后立即退出，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()) ) 

---

或者用一个唯一的名字定义你自己的Array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 4

您可以先从filterstrings 创建一个RegExp

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

如果有passedinstring，那么test

var isAvailable = regex.test( passedinstring ); 

Answer 5

我相信这会更简单、更短、更容易理解。

  const q = new RegExp(query, 'i');

  filteredUsers = users.filter((user: User) => {
    return (
      user.entity.short.match(q) ||
      user.firstname.match(q) ||
      user.lastname.match(q)
    );
  });

Answer 6

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

p>

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 7

使用toLowerCase() 修复了区分大小写的问题。比较时会将所有string 转换为小写。

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

Answer 8

我的选择是将 UPPER 与 UPPER 进行比较，或者将 UPPER 与 UPPER 进行比较，或者将两者与较低的进行比较（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

Answer 9

将filterstring和passedinstring转换为小写并比较

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 10

您可以简单地将传递的字符串转换为小写。

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