# zest

**Repository Path**: mirrors_jfromaniello/zest

## Basic Information

- **Project Name**: zest
- **Description**: An absurdly fast CSS selector engine.
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2020-09-25
- **Last Updated**: 2026-05-31

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Zest

__zest.js__ is a fast, lightweight, and extensible CSS selector engine.

Zest was designed to be very concise while still supporting CSS3/CSS4
selectors and remaining fast.

## Usage

``` js
zest('section! > div[title="hello" i] > :local-link /href/ h1');
```

## Benchmarks

Each selector run 1000 times on Google Chrome 13 beta (ms):

    benchmarking: `header > h1` 1000 times.
    zest: 13
    sizzle: 24
    native: 13
    benchmarking: `body > header > h1` 1000 times.
    zest: 16
    sizzle: 26
    native: 13
    benchmarking: `html a` 1000 times.
    zest: 45
    sizzle: 55
    native: 12
    benchmarking: `:first-child` 1000 times.
    zest: 44
    sizzle: 68
    native: 11
    benchmarking: `:only-child` 1000 times.
    zest: 49
    sizzle: 66
    native: 12
    benchmarking: `:not(a)` 1000 times.
    zest: 51
    sizzle: 125
    native: 12
    benchmarking: `h1 + time:last-child` 1000 times.
    zest: 15
    sizzle: 32
    native: 13
    benchmarking: `h1 + time[datetime]:last-child` 1000 times.
    zest: 21
    sizzle: 45
    native: 14
    benchmarking: `header > h1, :not(a)` 1000 times.
    zest: 72
    sizzle: 212
    native: 17
    benchmarking: `a[rel~="section"]` 1000 times.
    zest: 41
    sizzle: 54
    native: 11
    benchmarking: `a, h1` 1000 times.
    zest: 25
    sizzle: 55
    native: 11
    benchmarking: `:nth-child(2n+1)` 1000 times.
    zest: 82
    sizzle: 97
    native: 13

__NOTE:__ If you want to run these benchmarks yourself make sure to turn off
Sizzle's (and Zest's) `document.querySelectorAll` delegation mechanism,
otherwise you will be benchmarking against `document.querySelectorAll`.

Zest will cache compiled selectors if it can't delegate to
`document.querySelectorAll`, `document.getElementById`, or
`document.getElementsByClassName` (depending). __The benchmark tests you see
above were performed with the caching mechanism disabled. If caching were
enabled, Zest would be faster than the native `document.querySelectorAll`.__

## Install

``` bash
$ npm install zest.js
```

## Notes

Zest currently includes support for ender.js, Prototype, and jQuery.

__Unsupported Selectors:__ `:hover`, `:active`, `:link`, `:visited`, all pseudo
elements, and namespaces.

`:link`, `:visited`, and pseudo elements are unsupported for obvious reasons
(they don't work). `:hover` and `:active` aren't supported because they examine
a dynamic state, you should be binding to events for this (`:focus` is
supported, but there is no fallback for legacy browsers).

## Extension

Zest doesn't support (m)any non-standard selectors, but it is possible to add
your own.

### Adding a simple selector

Adding simple selectors is fairly straight forward. Only the addition of pseudo
classes and attribute operators is possible. (Adding your own "style" of
selector would require changes to the core logic.)

Here is an example of a custom `:name` selector which will match for an
element's `name` attribute: e.g. `h1:name(foo)`. Effectively an alias
for `h1[name=foo]`.

``` js
// if there was a parameter,
// it gets closured as `param`
zest.selectors[':name'] = function(param) {
  return function(el) {
    if (el.name === param) return true;
  };
};
```

__NOTE__: if you're pseudo-class does not take a parameter, there will be no
closure.

### Adding an attribute operator

``` js
// `attr` is the attribute
// `val` is the value to match
zest.operators['!='] = function(attr, val) {
  return attr !== val;
};
```

### Adding a combinator

Adding a combinator is a bit trickier. It may seem confusing at first because
the logic is upside-down. Zest interprets selectors from right to left.

Here is an example how a parent combinator could be implemented:

``` js
zest.combinators['<'] = function(test) {
  return function(el) { // `el` is the current element
    el = el.firstChild;
    while (el) {
      // return the relevant element
      // if it passed the test
      if (el.nodeType === 1 && test(el)) {
        return el;
      }
      el = el.nextSibling;
    }
  };
};
```

The `test` function tests whatever simple selectors it needs to look for, but
it isn't important what it does. The most important part is that you return
the relevant element once it's found.

## License

(c) Copyright 2011-2012, Christopher Jeffrey (MIT Licensed).
See LICENSE for more info.