<pre class="shiki github-dark shaku"><code>/** * @param {any} arg * @returns any */function undefinedToNull(arg) { if(typeof arg ==='undefined'||arg ==null) return null; if(typeof arg ==='object'){ if(Array.isArray(arg)){ return arg.map(undefinedToNull) } Object.keys(arg).map(key =&gt; { arg[key] = undefinedToNull(arg[key]) }) return arg; } return arg;}</code></pre>

Find the time complexity and space complexity yourself

One of the differences between null and undefined is how they are treated differently in JSON.stringify(). JSON.stringify({a: null}) // '{"a":null}'JS…