[Javascript] The JSON.stringify API

JSON

(JavaScript Object Notation) is a standard method to serialize JavaScript objects and is commonly used to transfer data from the server to the browser. The browser has a

JSON

API that allows you to serialize a JavaScript object or array into a

JSON

string. This API allows you to customize the serialization very specifically as well.

console.clear()

testValue()
testSpaces()
testFunctionReplacer()
testArrayReplacer()
testSymbolKeyedValues()
testNonEnumerableValue()
testToJSON()

console.log('Tests passed')

// function declarations
function testValue() {
var input = {
name: 'Kent C. Dodds',
username: 'kentcdodds',
}
var expected = '{"name":"Kent C. Dodds","username":"kentcdodds"}'
var result = JSON.stringify(input)

expect(result).toEqual(expected)
}

function testSpaces() {
var input = {
name: {
first: 'Kent',
middle: 'Christopher',
last: 'Dodds'
},
username: 'kentcdodds',
}
var expected = `{
"name": {
"first": "Kent",
"middle": "Christopher",
"last": "Dodds"
},
"username": "kentcdodds"
}`
var result = JSON.stringify(input, null, 2)

expect(result).toEqual(expected)
}

function testFunctionReplacer() {
var input = {
title: 'Gone with the Wind',
publishDate: new Date('1936-06-10'),
movieReleaseDate: new Date('1940-01-17'),
}

var expected = '{"title":"Gone with the Wind","publishDate":"1936-06-10","movieReleaseDate":"1940-01-17"}'

var result = JSON.stringify(input, replacer)

expect(result).toEqual(expected)

function replacer(key, value) {
// `this` is bound to the object in which the value was found
if (this[key] instanceof Date) {
return value.substring(0, 10)
}
return value
}
}

function testArrayReplacer() {
var input = [
{id: 3, title: 'Inside Out', rating: 98, genres: ['Animation', 'Kids & Family']},
{id: 6, title: 'The Hunger Games', rating: 84, genres: ['    Drama', 'Mystery & Suspense', 'Science Fiction & Fantasy']},
{id: 13, title: 'Catch Me If You Can', rating: 96, genres: ['Drama', 'Action & Adventure']},
]
var expected = '[{"id":3,"title":"Inside Out"},{"id":6,"title":"The Hunger Games"},{"id":13,"title":"Catch Me If You Can"}]'
var result = JSON.stringify(input, ['id', 'title'])

expect(result).toEqual(expected)
}

function testSymbolKeyedValues() {
var input = {foo: 'foo'}
var barSymbol = Symbol('bar')
input[barSymbol] = 'bar'

var expected = '{"foo":"foo"}'
var result = JSON.stringify(input)

expect(result).toEqual(expected)
}

function testNonEnumerableValue() {
var input = Object.create(null, {
theAnswer: {
value: 42,
enumerable: true
},
theQuestion: {
value: 'Who knows...',
enumerable: false
}
})

var expected = '{"theAnswer":42}'
var result = JSON.stringify(input)

expect(result).toEqual(expected)
}

function testToJSON() {
var input = {
name: {
first: 'Dave',
middle: 'James',
last: 'Smith',
toJSON: function(key) {
return {awesomeName: `The Awesome ${this.first} ${this.middle} ${this.last}`}
console.log(key, this)
},
},
username: 'djsmith42',
}

var expected = '{"name":{"awesomeName":"The Awesome Dave James Smith"},"username":"djsmith42"}'
var result = JSON.stringify(input)

expect(result).toEqual(expected)
}