Convert Hex Color to rgba with opacity

es5.js

/**
 * ECMA2015
 */
function convertHex(hexCode, opacity = 1){
    var hex = hexCode.replace('#', '');

    if (hex.length === 3) {
        hex = hex[0] + hex[0] + hex[1] + hex[1] + hex[2] + hex[2];
    }

    var r = parseInt(hex.substring(0,2), 16),
        g = parseInt(hex.substring(2,4), 16),
        b = parseInt(hex.substring(4,6), 16);

    /* Backward compatibility for whole number based opacity values. */
    if (opacity > 1 && opacity <= 100) {
        opacity = opacity / 100;   
    }
    
    return 'rgba('+r+','+g+','+b+','+opacity+')';
}

es6.js

/**
 * ECMA2016 / ES6
 */
const convertHexToRGBA = (hexCode, opacity = 1) => {  
    let hex = hexCode.replace('#', '');
    
    if (hex.length === 3) {
        hex = `${hex[0]}${hex[0]}${hex[1]}${hex[1]}${hex[2]}${hex[2]}`;
    }    
    
    const r = parseInt(hex.substring(0, 2), 16);
    const g = parseInt(hex.substring(2, 4), 16);
    const b = parseInt(hex.substring(4, 6), 16);
    
    /* Backward compatibility for whole number based opacity values. */
    if (opacity > 1 && opacity <= 100) {
        opacity = opacity / 100;   
    }

    return `rgba(${r},${g},${b},${opacity})`;
};

tests.js

describe('convertHexToRGBA', () => {
  test('accepts a hex value of 6 numbers and returns a rgba color string', () => {
    expect(convertHexToRGBA('#F3F3F3')).toBe('rgba(243,243,243,1)')
  })
  
  test('accepts a hex value of 6 numbers with opacity of 1 and returns same color string', () => {
    expect(convertHexToRGBA('#000', 1)).toBe(convertHexToRGBA('#000'))
  })
  
  test('accepts a hex value of 6 numbers with opacity and returns a rgba color string', () => {
    expect(convertHexToRGBA('#000', 0.5)).toBe('rgba(0,0,0,0.5)')
  })
  
  test('accepts a hex value of 3 numbers and returns a rgba color string', () => {
    expect(convertHexToRGBA('#aaa')).toBe('rgba(170,170,170,1)')
  })
 
  test('accepts a hex value of 3 numbers with opacity and returns a rgba color string', () => {
    expect(convertHexToRGBA('#aaa', 0.5)).toBe('rgba(170,170,170,0.5)')
  })
  
  test('accepts a hex value of 3 numbers with opacity of 1 and returns same color string', () => {
    expect(convertHexToRGBA('#aaa', 1)).toBe(convertHexToRGBA('#aaa', 1))
  })
})

The tests won't work with the current code since the converter doesn't have a default value for the opacity and the opacity is divided by 100 so you won't get the proper values if you use 0 - 1.

const convertHexToRGBA = (hexCode, opacity = 1) => {
    let hex = hexCode.replace('#', '');
    
    if (hex.length === 3) {
        hex = `${hex[0]}${hex[0]}${hex[1]}${hex[1]}${hex[2]}${hex[2]}`;
    }    
    
    const r = parseInt(hex.substring(0, 2), 16);
    const g = parseInt(hex.substring(2, 4), 16);
    const b = parseInt(hex.substring(4, 6), 16);

    return `rgba(${r},${g},${b},${opacity})`;
};

If you want to use it with with the division:

• change the default value of opacity to 100
• change tests

describe('convertHexToRGBA', () => {
  test('accepts a hex value of 6 numbers and returns a rgba color string', () => {
    expect(convertHexToRGBA('#F3F3F3')).toBe('rgba(243,243,243,100)')
  })
  
  test('accepts a hex value of 6 numbers with opacity of 1 and returns same color string', () => {
    expect(convertHexToRGBA('#000', 100)).toBe(convertHexToRGBA('#000'))
  })
  
  test('accepts a hex value of 6 numbers with opacity and returns a rgba color string', () => {
    expect(convertHexToRGBA('#000', 50)).toBe('rgba(0,0,0,50)')
  })
  
  test('accepts a hex value of 3 numbers and returns a rgba color string', () => {
    expect(convertHexToRGBA('#aaa')).toBe('rgba(170,170,170,100)')
  })
  
  test('accepts a hex value of 3 numbers with opacity and returns a rgba color string', () => {
    expect(convertHexToRGBA('#aaa', 50)).toBe('rgba(170,170,170,50)')
  })
  
  test('accepts a hex value of 3 numbers with opacity of 1 and returns same color string', () => {
    expect(convertHexToRGBA('#aaa', 100)).toBe(convertHexToRGBA('#aaa', 100))
  })
})

Thank you friend! 🙏

@MrMightyNighty - Thanks for the tip. Updated to include change to decimal based parameters, but also added a backward compatibility layer so it should theoretically work both ways, as long as you don't expect 0.9/100 to work without using pure 0.009, but I don't see that happening.