EN
JavaScript - convert object to JSON with ordered properties
5 points
In this article we would like to show how in JavaScript create JSON from object that has ordered properties.
Quick solution:
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const isObject = (entry) => typeof entry === 'object';2
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const iterateKeys = (entry, callback) => {4
const keys = Object.keys(entry);5
for (const key of keys) {6
callback(key, entry[key]);7
};8
};9
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const findKeys = (entry) => {11
if (isObject(entry)) {12
const keys = [];13
const callback = (key, value) => {14
keys.push(key);15
if (isObject(value)) {16
iterateKeys(value, callback);17
}18
};19
iterateKeys(entry, callback);20
return keys.sort();21
}22
return null;23
};24
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const toJson = (object, indent) => {26
const keys = findKeys(object);27
return JSON.stringify(object, keys, indent);28
};29
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// Usage example:32
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const indent = ' ';34
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const object = {36
name: 'John', // <-------- it will be moved to 2nd position37
age: 25, // <-------- it will be moved to 1st position38
todos: [39
'Lectures',40
'Classes'41
]42
};43
const json = toJson(object, indent);44
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console.log(json);
The solution in below example sorts properies before stringify operation.
Practical example:
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const escapeText = (text) => {2
let result = '';3
for (let i = 0; i < text.length; ++i) {4
const code = text.charCodeAt(i);5
switch (code) {6
case 0x00: // \0 - NULL7
case 0x01: case 0x02: case 0x03: case 0x04:8
case 0x05: case 0x06: case 0x07: case 0x08:9
continue;10
case 0x09: // \t - TABULATOR11
result += '\\t';12
continue;13
case 0x0A: // \n - NEW LINE14
result += '\\n';15
continue;16
case 0x0B: case 0x0C:17
continue;18
case 0x0D: // \r - CARRIAGE RETURN19
result += '\\r';20
continue;21
case 0x0E: case 0x0F: case 0x10: case 0x11:22
case 0x12: case 0x13: case 0x14: case 0x15:23
case 0x16: case 0x17: case 0x18: case 0x19:24
case 0x1A: case 0x1B: case 0x1C: case 0x1D:25
case 0x1E: case 0x1F:26
continue;27
// allowed characters: 0x20 and 0x2128
case 0x22: // " - DOUBLE QUOTATION MARK29
result += '\\"';30
continue;31
// allowed characters: 0x23 - 0x2632
case 0x27: // ' - SINGLE QUOTATION MARK33
result += '\'';34
continue;35
// allowed characters: 0x28 - 0x5B36
case 0x5C: // \ - BACK SLASH37
result += '\\\\';38
continue;39
default:40
result += text[i];41
}42
}43
return result;44
};45
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const getType = (object) => {47
return Object.prototype.toString.call(object);48
};49
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const prettifyArray = (array, prefix, indent) => {51
let result = '[\n';52
for (let i = 0; i < array.length; ++i) {53
const value = prettifyEntry(array[i], prefix + indent, indent);54
if (i > 0) {55
result += ',\n'56
}57
result += prefix + indent + value;58
}59
return result + '\n' + prefix + ']';60
};61
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const prettifyObject = (object, prefix, indent) => {63
let result = '{\n';64
const keys = Object.keys(object);65
for (const key of keys.sort()) {66
const name = escapeText(key);67
const value = prettifyEntry(object[key], prefix + indent, indent);68
if (result.length > 2) {69
result += ',\n'70
}71
result += prefix + indent + '"' + name + '": ' + value;72
}73
return result + '\n' + prefix + '}';74
};75
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const prettifyEntry = (entry, prefix, indent) => {77
const type = getType(entry);78
switch(type) {79
case '[object Array]':80
return prettifyArray(entry, prefix, indent);81
case '[object Object]':82
return prettifyObject(entry, prefix, indent);83
case '[object Null]':84
return null;85
case '[object Boolean]':86
case '[object Number]':87
case '[object BigInt]':88
return entry;89
case '[object String]':90
return '"' + escapeText(entry) + '"';91
default:92
throw new Error(type + ' type is not permitted in json.');93
}94
};95
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const stringifyObject = (object, indent) => {97
return prettifyEntry(object, '', indent || '\t');98
};99
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// Usage example:101
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const indent = ' ';103
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const object = {105
"name": "John",106
"age": 25,107
"todos": [108
"Lectures",109
"Classes"110
]111
};112
const json = stringifyObject(object, indent);113
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console.log(json);
