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  • Truthy and Falsy Values and Equality Operators

      最近在学习JS.  有一些概念还希望跟大家分享出来

    Truthy and Falsy Values

    Falsy Values: undefined, null, 0, '', NaN(not a number)

    Truthy values: NOT falsy values

     var height;
        height = 0; // return else value
    
        var name;
        name = ''; // return else value
    
        var testNumber;
        testNumber = 1; // return if value
    
        if (height) {
            console.log("Variable is defined");
        } else {
            console.log("Variable has NOT been defined");
        }

    Equality Operators

    == 和 === 的区别

    === 是必须type 相同的情况下value 相同.

    e.g. 

        var number1;
        number1 = 1;
    
        var number2;
        number2 = 1;
    
        var isNumberSame;
        number1 === number2 ? isNumberSame = true : isNumberSame = false;
        console.log("Is 2 numbers same? " + isNumberSame)

    == 不考虑type的情况下只考虑value相同.

    e.g.

        var number1;
        number1 = 1;
    
        var number2;
        number2 = 1;
    
        var string1;
        string1 = "1";
    
        // var isNumberSame;
        // number1 === number2 ? isNumberSame = true : isNumberSame = false;
        // console.log("Is 2 numbers same? " + isNumberSame)
    
    
    
        if(number1 == string1)
        {
            console.log("The == operator does type ")
        }
        else{
            console.log("Error")
        }
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  • 原文地址:https://www.cnblogs.com/TheMiao/p/9734380.html
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