JSON Pretty Print Stringify

by Kushal Jayswal

CSS

pre {
    outline: 1px solid #ccc;
    padding: 5px;
    margin: 5px;
}
.string {
    color: green;
}
.number {
    color: darkorange;
}
.boolean {
    color: blue;
}
.null {
    color: magenta;
}
.key {
    color: red;
}

JavaScript

function output(inp) {
    document.body.appendChild(document.createElement('pre')).innerHTML = inp;
}

function syntaxHighlight(json) {
    json = json.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
    return json.replace(/("(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?|\b(true|false|null)\b|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?)/g, function (match) {
        var cls = 'number';
        if (/^"/.test(match)) {
            if (/:$/.test(match)) {
                cls = 'key';
            } else {
                cls = 'string';
            }
        } else if (/true|false/.test(match)) {
            cls = 'boolean';
        } else if (/null/.test(match)) {
            cls = 'null';
        }
        return '<span class="' + cls + '">' + match + '</span>';
    });
}

var obj = {
    a: 1,
    'b': 'foo',
    c: [false, 'false', null, 'null', {
        d: {
            e: 1.3e5,
            f: '1.3e5'
        }
    }]
};
var str = JSON.stringify(obj, undefined, 4);

output(str);
output(syntaxHighlight(str));