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Detailed code examples of how to determine whether objects are equal in javascript

伊谢尔伦Original: 2017-07-26 11:54:311889browse

We know that if two objects have even contents, JavaScript will judge that they are not equal. But sometimes, we just need to determine whether the contents of two objects are equal. So how should we do this and be considerate? For example, 0 and -0, null and undefined are not equal, and NaN and NaN are not equal by default. I wrote an isEqual method, taking many aspects into consideration. The code is as follows:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title></title>
  </head>
  <body>
  </body>
<script type="text/javascript">
//isEqual：判断两个对象是否键值对应相等
function isEqual(a,b){
  //如果a和b本来就全等
  if(a===b){
    //判断是否为0和-0
    return a !== 0 || 1/a ===1/b;
  }
  //判断是否为null和undefined
  if(a==null||b==null){
    return a===b;
  }
  //接下来判断a和b的数据类型
  var classNameA=toString.call(a),
    classNameB=toString.call(b);
  //如果数据类型不相等，则返回false
  if(classNameA !== classNameB){
    return false;
  }
  //如果数据类型相等，再根据不同数据类型分别判断
  switch(classNameA){
    case &#39;[object RegExp]&#39;:
    case &#39;[object String]&#39;:
    //进行字符串转换比较
    return &#39;&#39; + a ===&#39;&#39; + b;
    case &#39;[object Number]&#39;:
    //进行数字转换比较,判断是否为NaN
    if(+a !== +a){
      return +b !== +b;
    }
    //判断是否为0或-0
    return +a === 0?1/ +a === 1/b : +a === +b;
    case &#39;[object Date]&#39;:
    case &#39;[object Boolean]&#39;:
    return +a === +b;
  }
  //如果是对象类型
  if(classNameA == &#39;[object Object]&#39;){
    //获取a和b的属性长度
    var propsA = Object.getOwnPropertyNames(a),
      propsB = Object.getOwnPropertyNames(b);
    if(propsA.length != propsB.length){
      return false;
    }
    for(var i=0;i<propsA.length;i++){
      var propName=propsA[i];
      //如果对应属性对应值不相等，则返回false
      if(a[propName] !== b[propName]){
        return false;
      }
    }
    return true;
  }
  //如果是数组类型
  if(classNameA == &#39;[object Array]&#39;){
    if(a.toString() == b.toString()){
      return true;
    }
    return false;
  }
}
//test
var obj1={name:"liu",age:22};
var obj2={name:"liu",age:22};
var obj3={name:"liu",age:33};
var state1=isEqual(obj1,obj2);
var state2=isEqual(obj1,obj3);
console.log(state1);//true
console.log(state2);//false
var state3=isEqual(null,undefined);
console.log(state3);//false
var state4=isEqual(NaN,NaN);
console.log(state4);//true
var arr1=[1,2,3];
var arr2=[1,2,3];
var arr3=[1,23];
var state5=isEqual(arr1,arr2);
console.log(state5);//true
var state6=isEqual(arr1,arr3);
console.log(state6);//false
</script>
</html>

The running effect diagram is as follows:

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