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;
}
