Pretty-printing JSON can enhance readability by introducing indentation, whitespace, and potentially colors or font styles. Here are two approaches:
Built-in Pretty-Printing
JavaScript's JSON.stringify() function provides native pretty-printing capabilities. Pass the third argument as a spacing level:
var str = JSON.stringify(obj, null, 2); // spacing level = 2
Syntax Highlighting with Regular Expressions
For syntax highlighting, you can use regular expressions to color-code different JSON elements:
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>'; }); }
Complete Example
Here's a full snippet that demonstrates both methods:
<div class="snippet" data-lang="js" data-hide="true" data-console="false" data-babel="false"> <div class="snippet-code snippet-currently-hidden"> <pre class="snippet-code-js lang-js prettyprint-override">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));
pre {outline: 1px solid #ccc; padding: 5px; margin: 5px; } .string { color: green; } .number { color: darkorange; } .boolean { color: blue; } .null { color: magenta; } .key { color: red; }
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