<pre class="shiki github-dark shaku"><code>/** * @param {any} data * @return {string} */function detectType(data) { // your code here const tag = Object.prototype.toString.call(data) // '[object Undefined]' const matches = tag.match(/\[object (\w+)\]/) if (matches) { return matches[1].toLowerCase() } throw new Error('unexpected data type')}</code></pre>

Object.prototype.toString

This is an easy problem. For all the basic data types in JavaScript, how could you write a function to detect the type of arbitrary data? Besides basi…