[IsJson hasJsonStructure safeJsonParse test] #JavaScript #TestHelper

isJson.js

/**
 * https://stackoverflow.com/questions/9804777/how-to-test-if-a-string-is-json-or-not
 */
const isJson = function isJson(item) {
    if ( Array.isArray(item)) return false;
    if ( Buffer.isBuffer(item)) return false;
    // by doing this, JSON.parse(1234) or JSON.parse(0) or JSON.parse(false) or JSON.parse(null) are invalid.
    item = typeof item !== 'string' ? JSON.stringify(item) : item;
    try {
        item = JSON.parse(item);
    } catch (e) {
        return false;
    }
    return (typeof item === 'object' && item !== null);
};
const hasJsonStructure = function hasJsonStructure(str) {
    if (typeof str !== 'string') return false;
    try {
        const result = JSON.parse(str);
        return Object.prototype.toString.call(result) === '[object Object]'
            || Array.isArray(result);
    } catch (err) {
        return false;
    }
};

const safeJsonParse = function safeJsonParse(str) {
    try {
        return [null, JSON.parse(str)];
    } catch (err) {
        return [err];
    }
};

[
    null,
        undefined,
        true,
        false,
        1,
        -7,
        5.5,
        -46.23,
        '',
        'this is a test',
        [],
        [1,2,3,4],
        ['a','b','c'],
        new Array(),
        new Array(10),
        new Array([1,2,3,4]),
        new Array(['a','b','c']),
        new Buffer(3),
        new Buffer('this is a test', 'utf8'),
        new Number(),
        new Number(1),
        new Number(-7),
        new Number(5.5),
        new Number(-46.23),
].forEach(subject=>console.log(`isJson(${subject})=${isJson(subject)}`));



[
    '',
    ' ',
    JSON.stringify({a:'1',b:['a','b','c']}),
    JSON.stringify(['a','b','c']),
    JSON.stringify([1,2,3,4]),
].forEach(subject=>console.log(`isJson(${subject})=${isJson(subject)}`));