To iterate array keys in JavaScript, we use the Object.keys method to get an array of string keys from the array.

For instance, we write

const array = [];
widthRange[46] = { sel: 46, min: 0, max: 52 };
widthRange[66] = { sel: 66, min: 52, max: 70 };
widthRange[90] = { sel: 90, min: 70, max: 94 };
const keys = Object.keys(array);

to call Object.keys with array to return an array of indexes of the array array.