Detailed explanation of the method of determining whether two objects are equal in JS

Strict equality operator (===)

use===The operator can compare whether two objects refer to the same object. If two variables refer to the same object, they are equal, otherwise they are not equal. For example:

const obj1 = { a: 1 };
const obj2 = { a: 1 };
const obj3 = obj1;

(obj1 === obj2); // false
(obj1 === obj3); // true

In the above example,obj1andobj2The attribute values ​​of the same, but they are different objects, so their===Compare backfalse. andobj1andobj3References to the same object, they are equal, soobj1 === obj3returntrue。

Here is a strict comparison, and the reference address and attribute name attribute values ​​must correspond one by one.

Comparison of object properties

If you just need to compare the properties of two objects equal (not compare reference addresses), you can use loop orMethod to get a list of object properties and compare their values. For example:

function isObjectEqual(obj1, obj2) {
  const obj1Keys = (obj1);
  const obj2Keys = (obj2);

  if ( !== ) {
    return false;
  }

  for (let key of obj1Keys) {
    if (obj1[key] !== obj2[key]) {
      return false;
    }
  }

  return true;
}

const obj1 = { a: 1, b: "hello" };
const obj2 = { a: 1, b: "world" };
const obj3 = { a: 1, b: "hello" };

(isObjectEqual(obj1, obj2)); // false
(isObjectEqual(obj1, obj3)); // true

In the above example,isObjectEqualFunction comparisonobj1andobj2and return the property value offalseBecause of theirbThe values ​​of the attributes are not equal. andisObjectEqual(obj1, obj3)returntrue, because all their attribute values ​​are equal.

Use Lodash and other tool libraries to determine whether two objects are equal

You can use LodashisEqualMethod (reference address is not compared).isEqualThe method recursively compares whether the property values ​​of the two objects are equal, including nested objects and arrays.

const obj1 = { a: 1, b: { c: 2 } };
const obj2 = { a: 1, b: { c: 2 } };
const obj3 = { a: 1, b: { c: 3 } };

(_.isEqual(obj1, obj2)); // true
(_.isEqual(obj1, obj3)); // false

In the above example,_.isEqual(obj1, obj2)returntrue, because all their attribute values ​​are equal, including nested objects. and_.isEqual(obj1, obj3)returnfalseBecause of theirThe values ​​of the attributes are not equal.

method

If your object contains only simple types (such as numbers, strings, booleans, and null) and other objects or arrays, you can useMethods convert objects into strings and then compare these strings (or do not compare reference addresses). For example:

const obj1 = { a: 1, b: "hello", c: true };
const obj2 = { a: 1, b: "hello", c: true };
const obj3 = { a: 1, b: "world", c: true };

((obj1) === (obj2)); // true
((obj1) === (obj3)); // false

In the above example,(obj1)and(obj2)Both return the same string, so their comparison returnstrue. and(obj1)and(obj3)Returns different strings, so comparison returnsfalse。

It should be noted that this method is only suitable for simple types and nested objects or arrays, because it cannot handle cases where objects contain types such as functions, regular expressions, and Date.

Use the () method

It's with===Operators are similar, but there are some special cases, such as(+0, -0)returnfalse,and===Operator returntrue。

const obj1 = { a: 1 };
const obj2 = { a: 1 };
const obj3 = obj1;

((obj1, obj2)); // false
((obj1, obj3)); // true

In the above example,(obj1, obj2)returnfalse,becauseobj1andobj2are two different objects, and(obj1, obj3)returntrue,becauseobj1andobj3References to the same object.

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