Created
October 31, 2018 16:27
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invertValueArrays
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import * as _ from 'lodash'; | |
// | |
// I couldn't figure out a clean way to write nor name this function. It's | |
// similar to lodash's "invertBy" except the values are arrays of strings. | |
// | |
// It's easiest examplained by example | |
// | |
// input | |
// { | |
// key1: ['val1', 'val2'], | |
// key2: ['val3', 'val1'], | |
// } | |
// | |
// output | |
// { | |
// val1: ['key1', 'key2'], | |
// val2: ['key1'], | |
// val3: ['key2'], | |
// val4: ['key2'], | |
// } | |
// | |
// I use this below to create a map of supported file extensions to parser | |
// names, which creates a helpful error message to detect duplicate file | |
// extensions handlers. | |
// | |
export const invertValueArrays = ( | |
result: { [propName: string]: string[] }, | |
valueArray: string[], | |
key: string | |
): { [propName: string]: string[] } => { | |
return valueArray.reduce((innerResult, value) => { | |
if (innerResult[value]) { | |
innerResult[value].push(key); | |
} else { | |
_.set(innerResult, value, [key]); | |
} | |
return innerResult; | |
}, result); | |
}; |
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