takeWhile.js

const arr = [ ... ]; // なにか配列
const pred = e => ...; // なにか述語
             
const {result} = arr.reduce((acc, cur) => {
    if (acc.finished) { return acc; }
    acc.finished = !pred(cur);
    if (acc.finished) { return acc; }
    acc.result.push(cur);
    return acc;
  }, {result: [], finished: false});