phpjs/_octopress/source/functions/prev/index.markdown

php.js offers community built php functions in javascript

---
layout: page
title: "JavaScript prev function"
comments: true
sharing: true
footer: true
alias:
- /functions/view/prev:492
- /functions/view/prev
- /functions/view/492
- /functions/prev:492
- /functions/492
---
<!-- Generated by Rakefile:build -->
A JavaScript equivalent of PHP's prev

{% codeblock array/prev.js lang:js https://raw.github.com/kvz/phpjs/master/functions/array/prev.js raw on github %}
function prev (arr) {
  // From: http://phpjs.org/functions
  // +   original by: Brett Zamir (http://brett-zamir.me)
  // %        note 1: Uses global: php_js to store the array pointer
  // *     example 1: transport = ['foot', 'bike', 'car', 'plane'];
  // *     example 1: prev(transport);
  // *     returns 1: false
  // BEGIN REDUNDANT
  this.php_js = this.php_js || {};
  this.php_js.pointers = this.php_js.pointers || [];
  var indexOf = function (value) {
    for (var i = 0, length = this.length; i < length; i++) {
      if (this[i] === value) {
        return i;
      }
    }
    return -1;
  };
  // END REDUNDANT
  var pointers = this.php_js.pointers;
  if (!pointers.indexOf) {
    pointers.indexOf = indexOf;
  }
  var arrpos = pointers.indexOf(arr);
  var cursor = pointers[arrpos + 1];
  if (pointers.indexOf(arr) === -1 || cursor === 0) {
    return false;
  }
  if (Object.prototype.toString.call(arr) !== '[object Array]') {
    var ct = 0;
    for (var k in arr) {
      if (ct === cursor - 1) {
        pointers[arrpos + 1] -= 1;
        return arr[k];
      }
      ct++;
    }
    // Shouldn't reach here
  }
  if (arr.length === 0) {
    return false;
  }
  pointers[arrpos + 1] -= 1;
  return arr[pointers[arrpos + 1]];
}
{% endcodeblock %}

 - [Raw function on GitHub](https://github.com/kvz/phpjs/blob/master/functions/array/prev.js)

Please note that php.js uses JavaScript objects as substitutes for PHP arrays, they are 
the closest match to this hashtable-like data structure. 

Please also note that php.js offers community built functions and goes by the 
[McDonald's Theory](https://medium.com/what-i-learned-building/9216e1c9da7d). We'll put online 
functions that are far from perfect, in the hopes to spark better contributions. 
Do you have one? Then please just: 

 - [Edit on GitHub](https://github.com/kvz/phpjs/edit/master/functions/array/prev.js)

### Example 1
This code
{% codeblock lang:js example %}
transport = ['foot', 'bike', 'car', 'plane'];
prev(transport);
{% endcodeblock %}

Should return
{% codeblock lang:js returns %}
false
{% endcodeblock %}


### Other PHP functions in the array extension
{% render_partial _includes/custom/array.html %}