How to determine whether two JSONs are equal in javascript

In daily programming work, judging whether two JSONs are equal is a very common problem. In JavaScript, we can determine whether two JSONs are equal by comparing property values ​​in the JSON objects. This article will discuss several ways to determine whether two JSONs are equal in JavaScript, including deep comparisons and shallow comparisons.

1. Shallow comparison

Shallow comparison is a relatively basic method, usually used to determine whether the attributes of two JSON objects are equal. Shallow comparisons only compare the top-level properties of a JSON object and do not recursively compare the objects' nested properties.

The following is a sample code that uses a shallow comparison method to determine whether two JSONs are equal:

function shallowEqual(obj1, obj2) {
  const keys1 = Object.keys(obj1);
  const keys2 = Object.keys(obj2);

  if (keys1.length !== keys2.length) {
    return false;
  }

  for (let i = 0; i < keys1.length; i++) {
    const key = keys1[i];
    if (obj1[key] !== obj2[key]) {
      return false;
    }
  }

  return true;
}

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

console.log(shallowEqual(obj1, obj2)); // false
console.log(shallowEqual(obj1, obj1)); // true

In the above sample code, we define a function named shallowEqual, which The function accepts two parameters obj1 and obj2, which are used to compare whether the two JSONs are equal. The function first uses the Object.keys() method to obtain the attribute name lists of obj1 and obj2, and then compares the two lists for equality. If not equal, the function returns false, otherwise iterates through each attribute of obj1 and compares whether its value is equal to the value of the corresponding attribute in obj2. If any of the values ​​are not equal, the function returns false, otherwise it returns true.

2. Deep comparison

Deep comparison is a more complex method, which is used to compare whether all attributes of two JSON objects are equal, including the nested attributes of the objects. When using the deep comparison method, we need to recursively traverse all properties of the JSON object and compare whether their values ​​are equal.

The following is a sample code that uses the deep comparison method to determine whether two JSONs are equal:

function deepEqual(obj1, obj2) {
  if (obj1 === obj2) {
    return true;
  }

  if (typeof obj1 !== typeof obj2) {
    return false;
  }

  if (Array.isArray(obj1) !== Array.isArray(obj2)) {
    return false;
  }

  if (typeof obj1 === "object" && obj1 !== null && obj2 !== null) {
    const keys1 = Object.keys(obj1);
    const keys2 = Object.keys(obj2);

    if (keys1.length !== keys2.length) {
      return false;
    }

    for (const key of keys1) {
      if (!obj2.hasOwnProperty(key)) {
        return false;
      }

      if (!deepEqual(obj1[key], obj2[key])) {
        return false;
      }
    }

    return true;
  }

  return obj1 === obj2;
}

const obj1 = { a: 1, b: ["foo", "bar"], c: { d: true } };
const obj2 = { a: 1, b: ["foo", "bar"], c: { d: true } };
const obj3 = { a: 1, b: ["foo", "bar"], c: { d: false } };

console.log(deepEqual(obj1, obj2)); // true
console.log(deepEqual(obj1, obj3)); // false

In the above sample code, we define a function named deepEqual, which Accepts two parameters obj1 and obj2, used to compare whether the two JSONs are equal. This function first determines whether obj1 and obj2 are exactly equal, and if so, returns true. Next, it checks if obj1 and obj2 are the same type, and returns false if not. It then checks if both obj1 and obj2 are of array type or object type and returns false if one is of array type and the other is of object type. If both JSON objects are of object type, use the Object.keys() method to get a list of their property names and compare the two lists for equality. Then the deepEqual function is called recursively for each attribute of obj1 to compare whether the values ​​of the corresponding attributes in obj1 and obj2 are equal. If the values ​​of any of the properties are not equal, the function returns false, otherwise it returns true.

Conclusion

Determining whether two JSONs are equal in JavaScript is a very useful operation. Whether using shallow comparisons or deep comparisons, there are many ways to solve this problem. If you only need to compare the top-level properties of a JSON object, use shallow comparison methods. If you need to compare all properties of a JSON object, including nested properties, use the deep comparison method to solve the problem. Whichever method you choose, remember to test your solution to make sure it correctly compares two JSON objects for equality.

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