list-flatten/src/index.js

Flatten an array or array-like list (non-recursive implementation).

import 'babel-polyfill'

export default
function flatten(array) {
    let currentArray = Array.from(array) // ES2015, in case we pass an array-like thing.
    let breadcrumbs = []
    let result = []

    let i=0
    while (currentArray) {

        if (currentArray[i] instanceof Array) {
            breadcrumbs.push({currentArray, i})
            currentArray = currentArray[i]
            i = -1
        }
        else { result.push(currentArray[i]) }

        let crumb = null
        while ( currentArray && i === currentArray.length - 1 ) {
            crumb = breadcrumbs.pop()
            currentArray = crumb ? crumb.currentArray : null
            i = crumb ? crumb.i : null
        }

        i+=1
    }

    return result
}