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This article will explain in detail how to use JSON.stringify for you. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

Basics

The JSON.stringify method takes a variable and converts it to a JSON representation.

Const boy = {name: 'John', age: 23}; JSON.stringify (boy); / / {"name": "John", "age": 23}

JSON is a pure string, which is essentially a subset of JS, so not all JS objects can be converted to JSON:

Const boy = {name: 'John', age: 23, hobbies: new Map ([[0,' coding'], [1, 'earn money']])} JSON.stringify (boy) / / {"name": "John", "age": 23, "hobbies": {}}

In the above example, the Map object is ignored and converted to a normal object. If the attribute is a function, then this attribute will be ignored, interested students can try.

The second parameter

JSON.stringify can receive the second parameter, which can be called a replacer replacement.

You can pass in an array of strings, and the properties in this array will be converted, just like a whitelist.

Const boy = {name: 'John', age: 23} JSON.stringify (boy, [' name']) / / {"name": "John"}

We can take advantage of this feature to convert only the properties that need to be converted and filter out long arrays, error objects, and so on.

This replacer parameter can also receive a function. This function iterates through the entire object, passing in keys and values, leaving you to decide how to replace them.

Const boy = {name: 'John', age: 23, hobbies: new Map ([0,' coding'], [1, 'earn money']])} JSON.stringify (boy, (key, value) = > {if (value instanceof Map) {return [... value.values ()]} return value}) / {"name": "John", "age": 23, "hobbies": ["coding", "earn money"]}

If you return undefined (not null), remove this property:

JSON.stringify (boy, (key, value) = > {if (typeof value = 'string') {return undefined} return value}) / / {"age": 23, "hobbies": {}}

The third parameter

The third parameter, space, controls the spacing of converted JSON strings.

If the parameter is a number, indent it with the space of the number:

JSON.stringify (boy, null, 2) / {/ / "name": "John", / / "age": 23 hobbies: {} / /}

If the parameter is a string, indent it with that string:

JSON.stringify (boy, null,'- -') / / {/-- "name": "John", / /-"age": 23 hobbies: {} / /}

ToJSON method

If the object we are converting has a toJSON method, we can customize the process by which we are serialized. Instead of serializing the object, you can return a new value from the method, and the value will be serialized instead of the original object.

Const boy = {name: 'John', age: 23, hobbies: new Map ([[0,' coding'], [1, 'earn money']]), toJSON () {return {name: `${this.name} (${this.age})`, favorite: this.hobbies.get (0)}} JSON.stringify (boy) / / {"name": "John (23)" "favorite": "coding"} this is the end of the article on "how to use JSON.stringify" Hope that the above content can be helpful to you, so that you can learn more knowledge, if you think the article is good, please share it for more people to see.

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