@ima/cli-plugin-less-constants
v2.1.2
Published
Plugin for @ima/cli to enable sharing constants between LESS and JS source files.
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@ima/cli-plugin-less-constants
Adds preprocessor which converts theme values defined in the JS file, to their LESS variable counterparts.
Can be used to share theme variables between JS and LESS files or even multiple npm packages to allow for easier overrides.
Installation
npm install @ima/cli-plugin-less-constants -D
Usage
// ./ima.config.js
const { LessConstantsPlugin } = require('@ima/cli-plugin-less-constants');
/**
* @type import('@ima/cli').ImaConfig
*/
module.exports = {
plugins: [
new LessConstantsPlugin({
entry: './app/config/theme.js'
})
],
};
Create theme.js file with constants definitions
Then export your LESS JS constants from the provided entry file, using the available units
helper functions, imported from the CLI plugin:
// ./app/config/theme.js
import { units, media } from '@ima/cli-plugin-less-constants/units';
export default {
bodyfontSize: units.rem(1),
headerHeight: units.px(120),
bodyWidth: units.vw(100),
greaterThanMobile: media.maxWidthMedia(360, 'screen'),
zIndexes: units.lessMap({
header: 100,
footer: 200,
body: 1,
}),
};
This produces the following output:
// ./build/less-constants/constants.less
@bodyfont-size: 1rem;
@header-height: 120px;
@body-width: 100vw;
@greater-than-mobile: ~"screen and (max-width: 360)";
@z-indexes: {
header: 100;
footer: 200;
body: 1;
}
Import generated constants.less
in globals
Finally don't forget to import the generated ./build/less-constants/constants.less
file in your ./app/less/globals.less
to have the variables available in all LESS files automatically without explicit import.
// ./app/less/globals.less
@import "../../build/less-constants/constants.less";
You can verify that your constants are actually used in your Less
files. The verify
option should include all directories that contain your Less files.
// ./ima.config.js
const { LessConstantsPlugin } = require('@ima/cli-plugin-less-constants');
/**
* @type import('@ima/cli').ImaConfig
*/
module.exports = {
plugins: [
new LessConstantsPlugin({
entry: './app/config/theme.js'
verify: ['./app']
})
],
};
Usage in JavaScript
Since every unit returns Unit
object, you can always access it's value through the .valueOf()
method or use the CSS interpreted value by calling .toString()
.
import { headerHeight } from 'app/config/theme.js';
export default function ThemeComponent({ children, title, href }) {
return (
<div>
Header height has an absolute value of: {headerHeight.valueOf()} {/* 120 */},
while it's CSS value is: {headerHeight.toString()} {/* 120px */}
</div>
);
}
Info: The constants are generated only in the
preProcess
which runs just ones before the compilation. So make sure to restart the built manually, when you add any new constants, to allow for the regeneration of theconstants.less
file.
Options
new LessConstantsPlugin(options: {
entry: string;
output?: string;
});
entry
string
Path to the LESS constants JS file.
output
string
Optional custom output path, defaults to ./build/less-constants/constants.less
.
Units
The plugin provides unit functions for almost every unit available + some other helpers. Each helper returns Unit
object with following interface:
export interface Unit {
valueOf: () => string;
toString: () => string;
}
- Numeric values -
em
,ex
,ch
,rem
,lh
,rlh
,vw
,vh
,vmin
,vmax
,vb
,vi
,svw
,svh
,lvw
,lvh
,dvw
,dvh
,cm
,mm
,Q
,inches
,pc
,pt
,px
,percent
. - Color values -
hex
,rgb
,rgba
,hsl
,hsla
. - Media queries -
maxWidthMedia
,minWidthMedia
,minAndMaxWidthMedia
,maxHeightMedia
,minHeightMedia
. - LESS map helper -
lessMap
can be used to group together similar values in an "object-like" value.
Custom units
If you're missing any additional helpers, you can always define your own, either custom ones (as long as they adhere to the Unit
interface) or you can use the following helper:
import { asUnit } from '@ima/cli-plugin-less-constants/units';
function asUnit(
unit: string,
parts: (string | number)[],
template = '${parts}${unit}'
): Unit {
return {
__propertyDeclaration: true,
valueOf(): string {
return parts.length === 1 ? parts[0].toString() : this.toString();
},
toString(): string {
return template
.replace('${parts}', parts.join(','))
.replace('${unit}', unit);
},
};
}
For more information, take a look at the IMA.js documentation.