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var colorContrastChecker = require("color-contrast-checker")

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color-contrast-checker v1.5.0

This is an accessibility validator based on WCAG 2.0 standard for checking the color contrast.

Color Contast Checker

An accessibility checker tool for validating the color contrast based on WCAG 2.0 standard.

The formula (L1/L2) for contrast is based on [ISO-9241-3] and [ANSI-HFES-100-1988] standards as described here :

http://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef http://www.w3.org/TR/WCAG20/#contrast-ratiodef

It also supports shorthand color codes e.g #FFF or #000 etc.

https://www.w3.org/TR/2001/WD-css3-color-20010305#colorunits

Installation:

npm install color-contrast-checker

or using package.json

{
  "name": "my-app",
  ..
  "devDependencies": {
    ..
    "color-contrast-checker": "1.5.0"
  }
}

Then do npm install

Usage:

To check specific WCAG levels

var ccc = new ColorContrastChecker();

var color1 = "#FFFFFF";
var color2 = "#000000;

if (ccc.isLevelAA(color1, color2, 14)) {
    alert("Valid Level AA");
} else {
    alert("Invalid Contrast");
}

To check custom ratios

var ccc = new ColorContrastChecker();

var color1 = "#FFFFFF";
var color2 = "#000000;
var customRatio = 5.7;

// No need for font size, now that we are using a custom ratio.
// This is because we are no longer checking against WCAG requirements.
if (ccc.isLevelCustom(color1, color2, customRatio)) {
    alert("Above given ratio");
} else {
    alert("Invalid Contrast");
}

Advanced Usage:

You can pass pairs and get results:

    var pairs = [
        {
            'colorA': '#000000',
            'colorB': '#000000',  // All should fail
            'fontSize': 14
        },
        {
            'colorA': '#000000',
            'colorB': '#FFFFFF',  //All should pass
            'fontSize': 14
        },
        {
            'colorA': '#000000',
            'colorB': '#848484',  //AAA should fail
            'fontSize': 14
        },
        {
            'colorA': '#000000',
            'colorB': '#848484',  //All should pass (because of font)
            'fontSize': 19
        },
        {
            'colorA': '#000000',
            'colorB': '#757575',  //AA should pass AAA should fail
            'fontSize': 14
        },
        {
            'colorA': '#000000',
            'colorB': '#656565',  //All should fail
            'fontSize': 14
        }
    ];

    var results = ccc.checkPairs(pairs);

The result will look like this:

[
    {
        'WCAG_AA' : false,
        'WCAG_AAA': false
    },
    {
        'WCAG_AA' : true,
        'WCAG_AAA': true
    },
    {
        'WCAG_AA' : true,
        'WCAG_AAA': false
    },
    {
        'WCAG_AA' : true,
        'WCAG_AAA': true
    },
    {
        'WCAG_AA' : true,
        'WCAG_AAA': false
    },
    {
        'WCAG_AA' : false,
        'WCAG_AAA': false
    }
]

Tests

npm test

Contributing

In lieu of a formal style guide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code.

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