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
这是一个非常干净的CoffeeScript版本,你可以这样做:
Object::equals = (other) ->
typeOf = Object::toString
return false if typeOf.call(this) isnt typeOf.call(other)
return `this == other` unless typeOf.call(other) is '[object Object]' or
typeOf.call(other) is '[object Array]'
(return false unless this[key].equals other[key]) for key, value of this
(return false if typeof this[key] is 'undefined') for key of other
true
下面是测试:
describe "equals", ->
it "should consider two numbers to be equal", ->
assert 5.equals(5)
it "should consider two empty objects to be equal", ->
assert {}.equals({})
it "should consider two objects with one key to be equal", ->
assert {a: "banana"}.equals {a: "banana"}
it "should consider two objects with keys in different orders to be equal", ->
assert {a: "banana", kendall: "garrus"}.equals {kendall: "garrus", a: "banana"}
it "should consider two objects with nested objects to be equal", ->
assert {a: {fruit: "banana"}}.equals {a: {fruit: "banana"}}
it "should consider two objects with nested objects that are jumbled to be equal", ->
assert {a: {a: "banana", kendall: "garrus"}}.equals {a: {kendall: "garrus", a: "banana"}}
it "should consider two objects with arrays as values to be equal", ->
assert {a: ["apple", "banana"]}.equals {a: ["apple", "banana"]}
it "should not consider an object to be equal to null", ->
assert !({a: "banana"}.equals null)
it "should not consider two objects with different keys to be equal", ->
assert !({a: "banana"}.equals {})
it "should not consider two objects with different values to be equal", ->
assert !({a: "banana"}.equals {a: "grapefruit"})
其他回答
这是一个经典的javascript问题!我创建了一个方法来检查深度对象是否相等,其特性是能够从比较中选择要忽略的属性。 参数是要比较的两个对象,加上一个可选的字符串化属性-忽略相对路径数组。
function isObjectEqual( o1, o2, ignorePropsArr=[]) {
// Deep Clone objects
let _obj1 = JSON.parse(JSON.stringify(o1)),
_obj2 = JSON.parse(JSON.stringify(o2));
// Remove props to ignore
ignorePropsArr.map( p => {
eval('_obj1.'+p+' = _obj2.'+p+' = "IGNORED"');
});
// compare as strings
let s1 = JSON.stringify(_obj1),
s2 = JSON.stringify(_obj2);
// return [s1==s2,s1,s2];
return s1==s2;
}
// Objects 0 and 1 are exact equals
obj0 = { price: 66544.10, RSIs: [0.000432334, 0.00046531], candles: {A: 543, B: 321, C: 4322}}
obj1 = { price: 66544.10, RSIs: [0.000432334, 0.00046531], candles: {A: 543, B: 321, C: 4322}}
obj2 = { price: 66544.12, RSIs: [0.000432334, 0.00046531], candles: {A: 543, B: 321, C: 4322}}
obj3 = { price: 66544.13, RSIs: [0.000432334, 0.00046531], candles: {A: 541, B: 321, C: 4322}}
obj4 = { price: 66544.14, RSIs: [0.000432334, 0.00046530], candles: {A: 543, B: 321, C: 4322}}
isObjectEqual(obj0,obj1) // true
isObjectEqual(obj0,obj2) // false
isObjectEqual(obj0,obj2,['price']) // true
isObjectEqual(obj0,obj3,['price']) // false
isObjectEqual(obj0,obj3,['price','candles.A']) // true
isObjectEqual(obj0,obj4,['price','RSIs[1]']) // true
如果两个对象的所有属性都具有相同的值,并且所有嵌套对象和数组都递归地具有相同的值,那么将它们视为相等是很有用的。我也认为以下两个对象是相等的:
var a = {p1: 1};
var b = {p1: 1, p2: undefined};
类似地,数组可以有“缺失”元素和未定义的元素。我也会同样对待它们:
var c = [1, 2];
var d = [1, 2, undefined];
函数:实现等式定义的函数:
function isEqual(a, b) {
if (a === b) {
return true;
}
if (generalType(a) != generalType(b)) {
return false;
}
if (a == b) {
return true;
}
if (typeof a != 'object') {
return false;
}
// null != {}
if (a instanceof Object != b instanceof Object) {
return false;
}
if (a instanceof Date || b instanceof Date) {
if (a instanceof Date != b instanceof Date ||
a.getTime() != b.getTime()) {
return false;
}
}
var allKeys = [].concat(keys(a), keys(b));
uniqueArray(allKeys);
for (var i = 0; i < allKeys.length; i++) {
var prop = allKeys[i];
if (!isEqual(a[prop], b[prop])) {
return false;
}
}
return true;
}
源代码(包括辅助函数,generalType和uniqueArray): 这里是单元测试和测试运行器。
function isEqual(obj1, obj2){
type1 = typeof(obj1);
type2 = typeof(obj2);
if(type1===type2){
switch (type1){
case "object": return JSON.stringify(obj1)===JSON.stringify(obj2);
case "function": return eval(obj1).toString()===eval(obj2).toString();
default: return obj1==obj2;
}
}
return false;
}//have not tried but should work.
下面的一些解决方案在性能、功能和风格方面存在问题……它们没有经过充分的考虑,其中一些在不同的情况下失败了。我试图在自己的解决方案中解决这个问题,我非常感谢您的反馈:
http://stamat.wordpress.com/javascript-object-comparison/
//Returns the object's class, Array, Date, RegExp, Object are of interest to us
var getClass = function(val) {
return Object.prototype.toString.call(val)
.match(/^\[object\s(.*)\]$/)[1];
};
//Defines the type of the value, extended typeof
var whatis = function(val) {
if (val === undefined)
return 'undefined';
if (val === null)
return 'null';
var type = typeof val;
if (type === 'object')
type = getClass(val).toLowerCase();
if (type === 'number') {
if (val.toString().indexOf('.') > 0)
return 'float';
else
return 'integer';
}
return type;
};
var compareObjects = function(a, b) {
if (a === b)
return true;
for (var i in a) {
if (b.hasOwnProperty(i)) {
if (!equal(a[i],b[i])) return false;
} else {
return false;
}
}
for (var i in b) {
if (!a.hasOwnProperty(i)) {
return false;
}
}
return true;
};
var compareArrays = function(a, b) {
if (a === b)
return true;
if (a.length !== b.length)
return false;
for (var i = 0; i < a.length; i++){
if(!equal(a[i], b[i])) return false;
};
return true;
};
var _equal = {};
_equal.array = compareArrays;
_equal.object = compareObjects;
_equal.date = function(a, b) {
return a.getTime() === b.getTime();
};
_equal.regexp = function(a, b) {
return a.toString() === b.toString();
};
// uncoment to support function as string compare
// _equal.fucntion = _equal.regexp;
/*
* Are two values equal, deep compare for objects and arrays.
* @param a {any}
* @param b {any}
* @return {boolean} Are equal?
*/
var equal = function(a, b) {
if (a !== b) {
var atype = whatis(a), btype = whatis(b);
if (atype === btype)
return _equal.hasOwnProperty(atype) ? _equal[atype](a, b) : a==b;
return false;
}
return true;
};
为了比较简单的键/值对对象实例的键,我使用:
function compareKeys(r1, r2) {
var nloops = 0, score = 0;
for(k1 in r1) {
for(k2 in r2) {
nloops++;
if(k1 == k2)
score++;
}
}
return nloops == (score * score);
};
一旦比较了键,一个简单的for. in循环就足够了。
复杂度是O(N*N), N是键的个数。
我希望/猜测我定义的对象不会拥有超过1000个属性…