How does JavaScript determine the authenticity of data in json (code example)

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During the project development process, it is often necessary to process json data. During the processing, it is inevitable to judge whether the data is true or false. Here are a few examples summarized for use

json data

const json = {
    a: null,
    b: '',
    c: 'c',
    d: {
        e: 21,
        f: true,
        g: false
    },
    h:1,
    i:0
}

null

let v = json.a
console.log(v)
if (v) {
    console.log('真')
} else {
    console.log('假')
}

Output:
null
False

Empty string

let v = json.b
console.log(v)
if (v) {
    console.log('真')
} else {
    console.log('假')
}

Output:

False

Number 1

let v = json.h
console.log(v)
if (v) {
    console.log('真')
} else {
    console.log('假')
}

Output:
1
True

Number 0

let v = json.i
console.log(v)
if (v) {
    console.log('真')
} else {
    console.log('假')
}

Output:
0
False

Numbers other than numbers 0 and 1

let v = json.d.e
console.log(v)
if (v) {
    console.log('真')
} else {
    console.log('假')
}

Output:
21
True

. Not in the first layer of the object The attribute name

let v = json.j
console.log(v)
if (v) {
    console.log('真')
} else {
    console.log('假')
}

Output:
undefined
false

. The attribute name

let v = json.j.x
console.log(v)
if (v) {
    console.log('真')
} else {
    console.log('假')
}

that is not in the second layer of the object reports an exception, the reason is json.j is undefined If you continue to click, an error will be reported

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