严格相等运算符将告诉您两个对象类型是否相等。然而,是否有一种方法来判断两个对象是否相等,就像Java中的哈希码值一样?
堆栈溢出问题JavaScript中有hashCode函数吗?类似于这个问题,但需要一个更学术的答案。上面的场景说明了为什么有必要有一个,我想知道是否有等效的解决方案。
严格相等运算符将告诉您两个对象类型是否相等。然而,是否有一种方法来判断两个对象是否相等,就像Java中的哈希码值一样?
堆栈溢出问题JavaScript中有hashCode函数吗?类似于这个问题,但需要一个更学术的答案。上面的场景说明了为什么有必要有一个,我想知道是否有等效的解决方案。
当前回答
我不知道是否有人发布过类似的东西,但这是我做的一个检查对象相等的函数。
function objectsAreEqual(a, b) {
for (var prop in a) {
if (a.hasOwnProperty(prop)) {
if (b.hasOwnProperty(prop)) {
if (typeof a[prop] === 'object') {
if (!objectsAreEqual(a[prop], b[prop])) return false;
} else {
if (a[prop] !== b[prop]) return false;
}
} else {
return false;
}
}
}
return true;
}
而且,它是递归的,所以它也可以检查深度相等,如果你这么称呼它的话。
其他回答
这是我的版本。它正在使用new Object。ES5中引入的keys特性以及+、+和+的想法/测试:
function objectEquals(x, y) { 'use strict'; if (x === null || x === undefined || y === null || y === undefined) { return x === y; } // after this just checking type of one would be enough if (x.constructor !== y.constructor) { return false; } // if they are functions, they should exactly refer to same one (because of closures) if (x instanceof Function) { return x === y; } // if they are regexps, they should exactly refer to same one (it is hard to better equality check on current ES) if (x instanceof RegExp) { return x === y; } if (x === y || x.valueOf() === y.valueOf()) { return true; } if (Array.isArray(x) && x.length !== y.length) { return false; } // if they are dates, they must had equal valueOf if (x instanceof Date) { return false; } // if they are strictly equal, they both need to be object at least if (!(x instanceof Object)) { return false; } if (!(y instanceof Object)) { return false; } // recursive object equality check var p = Object.keys(x); return Object.keys(y).every(function (i) { return p.indexOf(i) !== -1; }) && p.every(function (i) { return objectEquals(x[i], y[i]); }); } /////////////////////////////////////////////////////////////// /// The borrowed tests, run them by clicking "Run code snippet" /////////////////////////////////////////////////////////////// var printResult = function (x) { if (x) { document.write('<div style="color: green;">Passed</div>'); } else { document.write('<div style="color: red;">Failed</div>'); } }; var assert = { isTrue: function (x) { printResult(x); }, isFalse: function (x) { printResult(!x); } } assert.isTrue(objectEquals(null,null)); assert.isFalse(objectEquals(null,undefined)); assert.isFalse(objectEquals(/abc/, /abc/)); assert.isFalse(objectEquals(/abc/, /123/)); var r = /abc/; assert.isTrue(objectEquals(r, r)); assert.isTrue(objectEquals("hi","hi")); assert.isTrue(objectEquals(5,5)); assert.isFalse(objectEquals(5,10)); assert.isTrue(objectEquals([],[])); assert.isTrue(objectEquals([1,2],[1,2])); assert.isFalse(objectEquals([1,2],[2,1])); assert.isFalse(objectEquals([1,2],[1,2,3])); assert.isTrue(objectEquals({},{})); assert.isTrue(objectEquals({a:1,b:2},{a:1,b:2})); assert.isTrue(objectEquals({a:1,b:2},{b:2,a:1})); assert.isFalse(objectEquals({a:1,b:2},{a:1,b:3})); assert.isTrue(objectEquals({1:{name:"mhc",age:28}, 2:{name:"arb",age:26}},{1:{name:"mhc",age:28}, 2:{name:"arb",age:26}})); assert.isFalse(objectEquals({1:{name:"mhc",age:28}, 2:{name:"arb",age:26}},{1:{name:"mhc",age:28}, 2:{name:"arb",age:27}})); Object.prototype.equals = function (obj) { return objectEquals(this, obj); }; var assertFalse = assert.isFalse, assertTrue = assert.isTrue; assertFalse({}.equals(null)); assertFalse({}.equals(undefined)); assertTrue("hi".equals("hi")); assertTrue(new Number(5).equals(5)); assertFalse(new Number(5).equals(10)); assertFalse(new Number(1).equals("1")); assertTrue([].equals([])); assertTrue([1,2].equals([1,2])); assertFalse([1,2].equals([2,1])); assertFalse([1,2].equals([1,2,3])); assertTrue(new Date("2011-03-31").equals(new Date("2011-03-31"))); assertFalse(new Date("2011-03-31").equals(new Date("1970-01-01"))); assertTrue({}.equals({})); assertTrue({a:1,b:2}.equals({a:1,b:2})); assertTrue({a:1,b:2}.equals({b:2,a:1})); assertFalse({a:1,b:2}.equals({a:1,b:3})); assertTrue({1:{name:"mhc",age:28}, 2:{name:"arb",age:26}}.equals({1:{name:"mhc",age:28}, 2:{name:"arb",age:26}})); assertFalse({1:{name:"mhc",age:28}, 2:{name:"arb",age:26}}.equals({1:{name:"mhc",age:28}, 2:{name:"arb",age:27}})); var a = {a: 'text', b:[0,1]}; var b = {a: 'text', b:[0,1]}; var c = {a: 'text', b: 0}; var d = {a: 'text', b: false}; var e = {a: 'text', b:[1,0]}; var i = { a: 'text', c: { b: [1, 0] } }; var j = { a: 'text', c: { b: [1, 0] } }; var k = {a: 'text', b: null}; var l = {a: 'text', b: undefined}; assertTrue(a.equals(b)); assertFalse(a.equals(c)); assertFalse(c.equals(d)); assertFalse(a.equals(e)); assertTrue(i.equals(j)); assertFalse(d.equals(k)); assertFalse(k.equals(l)); // from comments on stackoverflow post assert.isFalse(objectEquals([1, 2, undefined], [1, 2])); assert.isFalse(objectEquals([1, 2, 3], { 0: 1, 1: 2, 2: 3 })); assert.isFalse(objectEquals(new Date(1234), 1234)); // no two different function is equal really, they capture their context variables // so even if they have same toString(), they won't have same functionality var func = function (x) { return true; }; var func2 = function (x) { return true; }; assert.isTrue(objectEquals(func, func)); assert.isFalse(objectEquals(func, func2)); assert.isTrue(objectEquals({ a: { b: func } }, { a: { b: func } })); assert.isFalse(objectEquals({ a: { b: func } }, { a: { b: func2 } }));
是的,另一个答案……
Object.prototype.equals = function (object) { if (this.constructor !== object.constructor) return false; if (Object.keys(this).length !== Object.keys(object).length) return false; var obk; for (obk in object) { if (this[obk] !== object[obk]) return false; } return true; } var aaa = JSON.parse('{"name":"mike","tel":"1324356584"}'); var bbb = JSON.parse('{"tel":"1324356584","name":"mike"}'); var ccc = JSON.parse('{"name":"mike","tel":"584"}'); var ddd = JSON.parse('{"name":"mike","tel":"1324356584", "work":"nope"}'); $("#ab").text(aaa.equals(bbb)); $("#ba").text(bbb.equals(aaa)); $("#bc").text(bbb.equals(ccc)); $("#ad").text(aaa.equals(ddd)); <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> aaa equals bbb? <span id="ab"></span> <br/> bbb equals aaa? <span id="ba"></span> <br/> bbb equals ccc? <span id="bc"></span> <br/> aaa equals ddd? <span id="ad"></span>
我使用这个可比函数来生成JSON可比的对象副本:
Var可比= o => (typeof o != '对象' || !o)?o: 种(o) .sort()。减少((c键)= > (c[主要]=可比(o(例子)),c), {}); / /演示: var = {1, c: 4 b:[2、3],d: {e:“5”,f:零}}; var b = {b:[2、3],c: 4 d: {f: null, e:“5”},答:1}; console.log (JSON.stringify(可比(a))); console.log (JSON.stringify(可比(b))); console.log(JSON.stringify(comparable(a)) == JSON.stringify(comparable(b))); < div id = " div " > < / div >
在测试中很方便(大多数测试框架都有一个is函数)。如。
is(JSON.stringify(comparable(x)), JSON.stringify(comparable(y)), 'x must match y');
如果捕捉到差异,则记录字符串,使差异可见:
x must match y
got {"a":1,"b":{"0":2,"1":3},"c":7,"d":{"e":"5","f":null}},
expected {"a":1,"b":{"0":2,"1":3},"c":4,"d":{"e":"5","f":null}}.
我建议不要使用散列或序列化(正如JSON解决方案所建议的那样)。如果需要测试两个对象是否相等,则需要定义相等的含义。这可能是两个对象中的所有数据成员都匹配,也可能是内存位置必须匹配(意味着两个变量在内存中引用同一个对象),或者每个对象中只有一个数据成员必须匹配。
最近我开发了一个对象,它的构造函数在每次创建实例时都会创建一个新的id(从1开始,加1)。该对象有一个isEqual函数,用于将该id值与另一个对象的id值进行比较,如果匹配则返回true。
在这种情况下,我定义“相等”的意思是id值匹配。假设每个实例都有一个唯一的id,这可以用来加强匹配对象也占用相同内存位置的想法。尽管这是不必要的。
在JavaScript for Objects中,当它们引用内存中的相同位置时,默认的相等运算符将产生true。
var x = {};
var y = {};
var z = x;
x === y; // => false
x === z; // => true
如果你需要一个不同的相等操作符,你需要添加一个equals(other)方法,或者类似的东西到你的类中,你的问题领域的细节将决定它的确切含义。
这里有一个扑克牌的例子:
function Card(rank, suit) {
this.rank = rank;
this.suit = suit;
this.equals = function(other) {
return other.rank == this.rank && other.suit == this.suit;
};
}
var queenOfClubs = new Card(12, "C");
var kingOfSpades = new Card(13, "S");
queenOfClubs.equals(kingOfSpades); // => false
kingOfSpades.equals(new Card(13, "S")); // => true