es6-comprehensions/src/utils.js

Transforms ES6 Array Comprehensions to ES5 compliant equivalent.

"use strict";

var utils = module.exports;

/**
 * This function is borrowed from https://github.com/square/es6-arrow-function/blob/master/lib/util.js
 *
 * Copyright (c) 2013, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

utils.guessTabWidth = function(source) {
  var counts = []; // Sparse array.
  var lastIndent = 0;

  source.split("\n").forEach(function(line) {
    var indent = /^\s*/.exec(line)[0].length;
    var diff = Math.abs(indent - lastIndent);
    counts[diff] = ~~counts[diff] + 1;
    lastIndent = indent;
  });

  var maxCount = -1;
  var result = 2;

  for (var tabWidth = 1;
       tabWidth < counts.length;
       tabWidth += 1) {
    if (tabWidth in counts &&
        counts[tabWidth] > maxCount) {
      maxCount = counts[tabWidth];
      result = tabWidth;
    }
  }

  return result;
};