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  • instanceof

     
    
     
    
    // primitive values
    var myNull = null;
    var myUndefined = undefined;
    var primitiveString1 = "string";
    var primitiveString2 = String('string');
    var primitiveNumber1 = 10;
    var primitiveNumber2 = Number('10');
    var primitiveBoolean1 = true;
    var primitiveBoolean2 = Boolean('true');
    
    console.log(typeof myNull); // logs object? WHAT? Be aware...
    console.log(typeof myUndefined); // logs undefined
    console.log(typeof primitiveString1, typeof primitiveString2); // logs string string
    console.log(typeof primitiveNumber1, typeof primitiveNumber2); // logs number number
    console.log(typeof primitiveBoolean1, typeof primitiveBoolean2); // logs boolean boolean
    
    // Complex Values
    var myNumber = new Number(23);
    var myString = new String('male');
    var myBoolean = new Boolean(false);
    var myObject = new Object();
    var myArray = new Array('foo', 'bar');
    var myFunction = new Function("x", "y", "return x * y");
    var myDate = new Date();
    var myRegExp = new RegExp('\bt[a-z]+\b');
    var myError = new Error('Crap!');
    
    console.log(typeof myNumber); // logs object
    console.log(typeof myString); // logs object
    console.log(typeof myBoolean); // logs object
    console.log(typeof myObject); // logs object
    console.log(typeof myArray); // logs object
    console.log(typeof myFunction); // logs function? WHAT? Be aware...
    console.log(typeof myDate); // logs object
    console.log(typeof myRegExp); // logs object? WHAT? Be aware...
    
    console.log(typeof myError); // logs object
    
    
    // instanceof 只适用于构造函数创建返回的复杂对象和实例
    
    // user-defined object constructor
    var CustomConstructor = function() {this.foo = 'bar';};
    
    //instantiate an instance of CustomConstructor
    var instanceOfCustomObject = new CustomConstructor(); 
    
    console.log(instanceOfCustomObject instanceof CustomConstructor); // logs true
    
    // works the same as a native object
    console.log(new Array('foo') instanceof Array) // logs true
    

      

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  • 原文地址:https://www.cnblogs.com/daqianduan/p/4378200.html
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