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
如何确定部分对象(partial <T>)等于typescript中的原始对象(T)。
function compareTwoObjects<T>(original: T, partial: Partial<T>): boolean {
return !Object.keys(partial).some((key) => partial[key] !== original[key]);
}
附注:最初我打算提出一个有答案的新问题。但这样的问题已经存在,并被标记为重复题。
其他回答
let std1 = {
name: "Abhijeet",
roll: 1
}
let std2 = {
name: "Siddharth",
roll: 2
}
console.log(JSON.stringify(std1) === JSON.stringify(std2))
下面是ES6/ES2015中使用函数式方法的解决方案:
const typeOf = x =>
({}).toString
.call(x)
.match(/\[object (\w+)\]/)[1]
function areSimilar(a, b) {
const everyKey = f => Object.keys(a).every(f)
switch(typeOf(a)) {
case 'Array':
return a.length === b.length &&
everyKey(k => areSimilar(a.sort()[k], b.sort()[k]));
case 'Object':
return Object.keys(a).length === Object.keys(b).length &&
everyKey(k => areSimilar(a[k], b[k]));
default:
return a === b;
}
}
这里有演示
当然,当我们在它的时候,我会抛出我自己对车轮的重新发明(我为辐条和使用的材料的数量感到自豪):
////////////////////////////////////////////////////////////////////////////////
var equals = function ( objectA, objectB ) {
var result = false,
keysA,
keysB;
// Check if they are pointing at the same variable. If they are, no need to test further.
if ( objectA === objectB ) {
return true;
}
// Check if they are the same type. If they are not, no need to test further.
if ( typeof objectA !== typeof objectB ) {
return false;
}
// Check what kind of variables they are to see what sort of comparison we should make.
if ( typeof objectA === "object" ) {
// Check if they have the same constructor, so that we are comparing apples with apples.
if ( objectA.constructor === objectA.constructor ) {
// If we are working with Arrays...
if ( objectA instanceof Array ) {
// Check the arrays are the same length. If not, they cannot be the same.
if ( objectA.length === objectB.length ) {
// Compare each element. They must be identical. If not, the comparison stops immediately and returns false.
return objectA.every(
function ( element, i ) {
return equals( element, objectB[ i ] );
}
);
}
// They are not the same length, and so are not identical.
else {
return false;
}
}
// If we are working with RegExps...
else if ( objectA instanceof RegExp ) {
// Return the results of a string comparison of the expression.
return ( objectA.toString() === objectB.toString() );
}
// Else we are working with other types of objects...
else {
// Get the keys as arrays from both objects. This uses Object.keys, so no old browsers here.
keysA = Object.keys( objectA );
keysB = Object.keys( objectB );
// Check the key arrays are the same length. If not, they cannot be the same.
if ( keysA.length === keysB.length ) {
// Compare each property. They must be identical. If not, the comparison stops immediately and returns false.
return keysA.every(
function ( element ) {
return equals( objectA[ element ], objectB[ element ] );
}
);
}
// They do not have the same number of keys, and so are not identical.
else {
return false;
}
}
}
// They don't have the same constructor.
else {
return false;
}
}
// If they are both functions, let us do a string comparison.
else if ( typeof objectA === "function" ) {
return ( objectA.toString() === objectB.toString() );
}
// If a simple variable type, compare directly without coercion.
else {
return ( objectA === objectB );
}
// Return a default if nothing has already been returned.
return result;
};
////////////////////////////////////////////////////////////////////////////////
它会尽可能快地返回false,但当然,对于一个差异嵌套很深的大对象,它可能不那么有效。在我自己的场景中,良好地处理嵌套数组非常重要。
希望它能帮助需要这种“轮子”的人。
只是想利用一些es6的特性来贡献我的对象比较版本。它不考虑订单。在将所有if/else转换为三元后,我带来了以下内容:
function areEqual(obj1, obj2) {
return Object.keys(obj1).every(key => {
return obj2.hasOwnProperty(key) ?
typeof obj1[key] === 'object' ?
areEqual(obj1[key], obj2[key]) :
obj1[key] === obj2[key] :
false;
}
)
}
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).