Function first

MathBox/mathbox-bundle.js:39436–39453

* Gets the first element or first `n` elements of an array. If a callback * is provided elements at the beginning of the array are returned as long * as the callback returns truey. The callback is bound to `thisArg` and * invoked with three arguments; (value, index, array). *

(array, callback, thisArg)

     * // => ['barney', 'fred']
     */
    function first(array, callback, thisArg) {
      var n = 0,
          length = array ? array.length : 0;

      if (typeof callback != 'number' && callback != null) {
        var index = -1;
        callback = lodash.createCallback(callback, thisArg, 3);
        while (++index < length && callback(array[index], index, array)) {
          n++;
        }
      } else {
        n = callback;
        if (n == null || thisArg) {
          return array ? array[0] : undefined;
        }
      }
      return slice(array, 0, nativeMin(nativeMax(0, n), length));
    }

    /**
     * Flattens a nested array (the nesting can be to any depth). If `isShallow`