js中如何比较两个对象是否相同？

方法一：通过JSON.stringify(obj)来判断两个对象转后的字符串是否相等

优点：用法简单，对于顺序相同的两个对象可以快速进行比较得到结果

缺点：这种方法有限制就是当两个对比的对象中key的顺序不是完全相同时会比较出错

方法二：对Object扩展一个方法chargeObjectEqual

// 
Object.prototype.chargeObjectEqual = function(obj){
// 当前Object对象
var propsCurr = Object.getOwnPropertyNames(this);
// 要比较的另外一个Object对象
var propsCompare = Object.getOwnPropertyNames(obj);
if (propsCurr.length != propsCompare.length) {
return false;
}
for (var i = 0,max = propsCurr.length; i < max; i++) {
var propName = propsCurr[i];
if (this[propName] !== obj[propName]) {
return false;
}
}
return true;
}

getOwnPropertyNames该方法可以将Object对象的第一层key获取到并返回一个由第一层key组成的数组。

优点：相对方法一进行了优化，可以应对不同顺序的Object进行比较，不用担心顺序不同而对比出错

缺点：从方法中可以看到只能获取到第一层的key组成的数组，当对象是复合对象时无法进行多层对象的比较

方法三：对象深度比较

function deepCompare(x, y) {
var i, l, leftChain, rightChain;

function compare2Objects(x, y) {
var p;

// remember that NaN === NaN returns false
// and isNaN(undefined) returns true
if (isNaN(x) && isNaN(y) && typeof x === 'number' && typeof y === 'number') {
return true;
}

// Compare primitives and functions. 
// Check if both arguments link to the same object.
// Especially useful on the step where we compare prototypes
if (x === y) {
return true;
}

// Works in case when functions are created in constructor.
// Comparing dates is a common scenario. Another built-ins?
// We can even handle functions passed across iframes
if ((typeof x === 'function' && typeof y === 'function') ||
(x instanceof Date && y instanceof Date) ||
(x instanceof RegExp && y instanceof RegExp) ||
(x instanceof String && y instanceof String) ||
(x instanceof Number && y instanceof Number)) {
return x.toString() === y.toString();
}

// At last checking prototypes as good as we can
if (!(x instanceof Object && y instanceof Object)) {
return false;
}

if (x.isPrototypeOf(y) || y.isPrototypeOf(x)) {
return false;
}

if (x.constructor !== y.constructor) {
return false;
}

if (x.prototype !== y.prototype) {
return false;
}

// Check for infinitive linking loops
if (leftChain.indexOf(x) > -1 || rightChain.indexOf(y) > -1) {
return false;
}

// Quick checking of one object being a subset of another.
// todo: cache the structure of arguments[0] for performance
for (p in y) {
if (y.hasOwnProperty(p) !== x.hasOwnProperty(p)) {
return false;
} else if (typeof y[p] !== typeof x[p]) {
return false;
}
}

for (p in x) {
if (y.hasOwnProperty(p) !== x.hasOwnProperty(p)) {
return false;
} else if (typeof y[p] !== typeof x[p]) {
return false;
}

switch (typeof(x[p])) {
case 'object':
case 'function':

leftChain.push(x);
rightChain.push(y);

if (!compare2Objects(x[p], y[p])) {
return false;
}

leftChain.pop();
rightChain.pop();
break;

default:
if (x[p] !== y[p]) {
return false;
}
break;
}
}

return true;
}

if (arguments.length < 1) {
return true; //Die silently? Don't know how to handle such case, please help...
// throw "Need two or more arguments to compare";
}

for (i = 1, l = arguments.length; i < l; i++) {

leftChain = []; //Todo: this can be cached
rightChain = [];

if (!compare2Objects(arguments[0], arguments[i])) {
return false;
}
}

return true;
}

深度对比两个对象是否完全相等，可以封装成一个组件方便随时调用。