Canvas fit letter height

.js

'use strict';

/*
    This function will resize a letter until it fits the specified height
    options:
        - height: the height to fit
        - precision: how much pixels +/-
        - size: the start font size
        - increment: the step of each iteration

 */

module.exports = function fitLetterHeight(options) {
    // height, precision, startSize, increment

    var tester = document.createElement('div');
    tester.style.visibility = 'hidden';
    tester.style.position = 'absolute';
    tester.textContent = 'M'; // M is usually the biggest letter
    document.body.appendChild(tester);

    var fit = false;
    var size = options.size - options.increment;

    while (!fit) {
        size += options.increment;
        tester.style.fontSize = size + 'px';
        var h = tester.offsetHeight;
        if (h >= options.height - options.precision) fit = true;
    }

    tester.parentNode.removeChild(tester);
    return size;
};