Function createPartial

lodash.js:5392–5413

* Creates a function that wraps `func` to invoke it with the `this` binding * of `thisArg` and `partials` prepended to the arguments it receives. * * @private * @param {Function} func The function to wrap. * @param {number} bitmask The bitmask flags. See `createWrap` for mor

(func, bitmask, thisArg, partials)

     * @returns {Function} Returns the new wrapped function.
     */
    function createPartial(func, bitmask, thisArg, partials) {
      var isBind = bitmask & WRAP_BIND_FLAG,
          Ctor = createCtor(func);

      function wrapper() {
        var argsIndex = -1,
            argsLength = arguments.length,
            leftIndex = -1,
            leftLength = partials.length,
            args = Array(leftLength + argsLength),
            fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;

        while (++leftIndex < leftLength) {
          args[leftIndex] = partials[leftIndex];
        }
        while (argsLength--) {
          args[leftIndex++] = arguments[++argsIndex];
        }
        return apply(fn, isBind ? thisArg : this, args);
      }
      return wrapper;
    }

    /**
     * Creates a `_.range` or `_.rangeRight` function.