package.cjs.debounce.js Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of underscore Show documentation

JavaScript's functional programming helper library.

The newest version!

var restArguments = require('./restArguments.js');
var now = require('./now.js');

// When a sequence of calls of the returned function ends, the argument
// function is triggered. The end of a sequence is defined by the `wait`
// parameter. If `immediate` is passed, the argument function will be
// triggered at the beginning of the sequence instead of at the end.
function debounce(func, wait, immediate) {
  var timeout, previous, args, result, context;

  var later = function() {
    var passed = now() - previous;
    if (wait > passed) {
      timeout = setTimeout(later, wait - passed);
    } else {
      timeout = null;
      if (!immediate) result = func.apply(context, args);
      // This check is needed because `func` can recursively invoke `debounced`.
      if (!timeout) args = context = null;
    }
  };

  var debounced = restArguments(function(_args) {
    context = this;
    args = _args;
    previous = now();
    if (!timeout) {
      timeout = setTimeout(later, wait);
      if (immediate) result = func.apply(context, args);
    }
    return result;
  });

  debounced.cancel = function() {
    clearTimeout(timeout);
    timeout = args = context = null;
  };

  return debounced;
}

module.exports = debounce;