Question 219495 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – Using argument as a part of "for each"

I try to create a simple script that will take RGB-16 colors and convert them to RGB-8. The script works, but for some reason I cannot figure out how to convert it to function so that it will work for two different palettes. Using palette.forEach causes an error. The problem seems to be easy to understand, but I cannot spot it out.

const system41 = [
  [65535, 65535, 65535],
  [64512, 62333,  1327],
  [65535, 25738,   652]
];

const system7 = [
  [65535, 65535, 52428],
  [65535, 52428, 39321],
  [52428, 39321, 26214]
];

function convert(palette) {
    palette.forEach((child) => {
        const rgb8 = child.map(value => Math.round(value / 257));
        document.querySelector('#' + palette).innerHTML += rgb8.join(', ') + 'n';
    });
}

convert('system41');
convert('system7');
<p>System 4.1 system colors</p>
<pre id="system41"></pre>

<p>System 7 icon colors</p>
<pre id="system7"></pre>
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2

Answers


  1. 0

    The first thing is that you should log the palette right after you define it in the function convert() you will see the reason why you can not achieve it.

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  2. 0

    Store your arrays in an object so you can perform string-wise lookups.

    const palettes = {
  system41: [
    [65535, 65535, 65535],
    [64512, 62333, 1327],
    [65535, 25738, 652]
  ],
  system7: [
    [65535, 65535, 52428],
    [65535, 52428, 39321],
    [52428, 39321, 26214]
  ]
};

function convert(palette) {
  palettes[palette].forEach((child) => {
    const rgb8 = child.map(value => Math.round(value / 257));
    document.querySelector('#' + palette).innerHTML += rgb8.join(', ') + 'n';
  });
}

convert('system41');
convert('system7');
    <p>System 4.1 system colors</p>
<pre id="system41"></pre>

<p>System 7 icon colors</p>
<pre id="system7"></pre>
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