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
这里有一个非常基本的方法来检查对象的“值是否相等”。
var john = {
occupation: "Web Developer",
age: 25
};
var bobby = {
occupation: "Web Developer",
age: 25
};
function isEquivalent(a, b) {
// Create arrays of property names
var aProps = Object.getOwnPropertyNames(a);
var bProps = Object.getOwnPropertyNames(b);
// If number of properties is different, objects are not equivalent
if (aProps.length != bProps.length) {
return false;
}
for (var i = 0; i < aProps.length; i++) {
var propName = aProps[i];
// If values of same property are not equal, objects are not equivalent
if (a[propName] !== b[propName]) {
return false;
}
}
// If we made it this far, objects are considered equivalent
return true;
}
// Outputs: true
console.log(isEquivalent(john, bobby));
演示 - JSFiddle
如你所见,为了检查对象的“值是否相等”,我们本质上必须遍历对象中的每个属性,以查看它们是否相等。虽然这个简单的实现适用于我们的示例,但有很多情况它无法处理。例如:
如果其中一个属性值本身就是一个对象呢? 如果属性值之一是NaN(中唯一的值 JavaScript不等于它自己?) 如果a有一个值为undefined的属性,而b没有呢 这个属性(因此计算为undefined?)
对于一个健壮的检查对象“值是否相等”的方法,最好依赖于一个经过良好测试的库,它涵盖了各种边缘情况,如下划线。
var john = {
occupation: "Web Developer",
age: 25
};
var bobby = {
occupation: "Web Developer",
age: 25
};
// Outputs: true
console.log(_.isEqual(john, bobby));
演示 - JSFiddle
其他回答
最简单和逻辑的解决方案,比较一切像对象,数组,字符串,Int…
JSON。stringify({a: val1}) == JSON。stringify ({a: val2})
注意:
你需要用你的Object替换val1和val2 对于对象,必须对两侧对象进行递归排序(按键)
如果你的问题是检查两个对象是否相等,那么这个函数可能会有用
function equals(a, b) {
const aKeys = Object.keys(a)
const bKeys = Object.keys(b)
if(aKeys.length != bKeys.length) {
return false
}
for(let i = 0;i < aKeys.length;i++) {
if(aKeys[i] != bKeys[i]) {
return false
}
}
for(let i = 0;i < aKeys.length;i++) {
if(a[aKeys[i]] != b[bKeys[i]]) {
return false
}
}
return true
}
first we check if the length of the list of keys of these objects is the same, if not we return false to check if two objects are equal they must have the same keys(=names) and the same values of the keys, so we get all the keys of objA, and objB and then we check if they are equal once we find that tow keys are not equal then we return false and then when all the keys are equal then we loop through one of the keys of one of the objects and then we check if they are equal once they are not we return false and after the two loops finished this means they are equal and we return true NOTE: this function works with only objects with no functions
你可以使用_。isEqual(obj1, obj2)来自underscore.js库。
这里有一个例子:
var stooge = {name: 'moe', luckyNumbers: [13, 27, 34]};
var clone = {name: 'moe', luckyNumbers: [13, 27, 34]};
stooge == clone;
=> false
_.isEqual(stooge, clone);
=> true
在这里查看官方文档:http://underscorejs.org/#isEqual
这取决于你对平等的定义。因此,作为类的开发人员,要由您来定义它们的相等性。
有时会使用一种情况,如果两个实例指向内存中的相同位置,则认为它们是“相等的”,但这并不总是您想要的。例如,如果我有一个Person类,如果两个Person对象具有相同的Last Name、First Name和Social Security Number(即使它们指向内存中的不同位置),我可能会认为它们是“相等的”。
另一方面,我们不能简单地说两个对象是相等的,如果它们的每个成员的值都相同,因为,有时,你并不想这样。换句话说,对于每个类,由类开发人员定义组成对象“标识”的成员并开发适当的相等操作符(通过重载==操作符或Equals方法)。
Saying that two objects are equal if they have the same hash is one way out. However you then have to wonder how the hash is calculated for each instance. Going back to the Person example above, we could use this system if the hash was calculated by looking at the values of the First Name, Last Name, and Social Security Number fields. On top of that, we are then relying on the quality of the hashing method (that's a huge topic on its own, but suffice it to say that not all hashes are created equal, and bad hashing methods can lead to more collisions, which in this case would return false matches).
Stringify两个对象并进行比较
返回(JSON.stringify(obj1) === = JSON.stringify(obj2))
这将返回true或false