判断两个数组是否相等

如何比较两个数组内容是否相等
一、不能通过 '==' 或者 '===' 来判断两个数组是否相等

alert([]==[]);    // false
alert([]===[]);   // false

因为JavaScript里面，数组是对象，上面等式是判断两个数组是否是同一个引用对象；在JavaScript里面是没有内置判断两个数组相等的方法。

二、不推荐通过转换成字符串

JSON.stringify(a1) == JSON.stringify(a2);
a1.toString() == a2.toString()

当数组中有数字1，另一个数组中是字符串'1'，如此两个数组就不相等了，此方法无效，反而会造成不必要的误导。

三、正确方法如下

// Warn if overriding existing method
if(Array.prototype.equals)
  console.warn("Overriding existing Array.prototype.equals. Possible causes: New API defines the method, there's a framework conflict or you've got double inclusions in your code.");
// attach the .equals method to Array's prototype to call it on any array
Array.prototype.equals = function (array) {
   // if the other array is a falsy value, return
   if (!array)  return false;

   // compare lengths - can save a lot of time 
  if (this.length != array.length)  return false;
  for (var i = 0, l = this.length; i < l; i++) {
      // Check if we have nested arrays
      if (this[i] instanceof Array && array[i] instanceof Array) {           
// recurse into the nested arrays
          if (!this[i].equals(array[i]))
              return false;       
      }           
      else if (this[i] != array[i]) { 
         // Warning - two different object instances will never be equal: {x:20} != {x:20}
         return false;   
      }           
  }       
  return true;
}
// Hide method from for-in loops
Object.defineProperty(Array.prototype, "equals", {enumerable: false});

四、两个对象是否相等

Object.prototype.equals = function(object2) {
    //For the first loop, we only check for types
    for (propName in this) {
        //Check for inherited methods and properties - like .equals itself
        //https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty
        //Return false if the return value is different
        if (this.hasOwnProperty(propName) != object2.hasOwnProperty(propName)) {
            return false;
        }
        //Check instance type
        else if (typeof this[propName] != typeof object2[propName]) {
            //Different types => not equal
            return false;
        }
    }
    //Now a deeper check using other objects property names
    for(propName in object2) {
        //We must check instances anyway, there may be a property that only exists in object2
            //I wonder, if remembering the checked values from the first loop would be faster or not 
        if (this.hasOwnProperty(propName) != object2.hasOwnProperty(propName)) {
            return false;
        }
        else if (typeof this[propName] != typeof object2[propName]) {
            return false;
        }
        //If the property is inherited, do not check any more (it must be equa if both objects inherit it)
        if(!this.hasOwnProperty(propName))
          continue;

        //Now the detail check and recursion

        //This returns the script back to the array comparing
        /**REQUIRES Array.equals**/
        if (this[propName] instanceof Array && object2[propName] instanceof Array) {
                   // recurse into the nested arrays
           if (!this[propName].equals(object2[propName]))
                        return false;
        }
        else if (this[propName] instanceof Object && object2[propName] instanceof Object) {
                   // recurse into another objects
                   //console.log("Recursing to compare ", this[propName],"with",object2[propName], " both named \""+propName+"\"");
           if (!this[propName].equals(object2[propName]))
                        return false;
        }
        //Normal value comparison for strings and numbers
        else if(this[propName] != object2[propName]) {
           return false;
        }
    }
    //If everything passed, let's say YES
    return true;
}

转自：https://www.cnblogs.com/-867259206/p/6795354.html