heading-level.js

Extract a valid heading level (1 - 6) from a tag name

headingLevel('h1'); //=> 1
headingLevel('H6'); //=> 6

headingLevel('h0'); //=> null
headingLevel('h7'); //=> null
headingLevel('div'); //=> null

// ... <h1 id='blog-title'></h1> ...
const elm = document.getElementById('blog-title');
headingLevel(elm.tagName); //=> 1

Installation

Install with package manager

npm

npm install heading-level

Bower

bower install heading-level

Standalone

Download the script file directly.

API

headingLevel(tagName)

Return: Number (1 - 6) or null

It returns a Number of heading level, when the argument is a heading tag name, such as "h3" and "H4".

It returns null when the argument is not a heading tag name.

It throws an error when the argument is not a String.

const result = [];
for(let i = 0; i <= 7; i++) {
  result.push(headingLevel('h' + i));
}

result; //=> [null, 1, 2, 3, 4, 5, 6, null]

const foo = document.createElement('h1');
const bar = document.createElement('div');

headingLevel(foo.tagName); //=> 1
headingLevel(bar.tagName); //=> null

License

Copyright (c) 2014 Shinnosuke Watanabe

Licensed under the MIT License.