How to determine whether a character is empty in javascript

Javascript method to determine whether a character is empty: first determine whether a character is empty, the code is [if(typeof res== "undefined" || res== null || res== "")]; Then call it through js.

The operating environment of this tutorial: Windows 7 system, JavaScript version 1.8.5, DELL G3 computer.

Javascript method to determine whether a character is empty:

js code:

//判断字符是否为空的方法
function IsEmpty(res){
    if(typeof res== "undefined" || res== null || res== ""){
        return true;
    }else{
        return false;
    }
}

js call:

if (!IsEmpty(value)) {
    alert(value);
}

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