framework/js/old/common/utils/computed.js

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/**
* The `computed` utility creates a function that will cache its output until
* any of the dependent values are dirty.
*
* @param {...String} dependentKeys The keys of the dependent values.
* @param {function} compute The function which computes the value using the
* dependent values.
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* @return {Function}
*/
export default function computed(...dependentKeys) {
const keys = dependentKeys.slice(0, -1);
const compute = dependentKeys.slice(-1)[0];
const dependentValues = {};
let computedValue;
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return function () {
let recompute = false;
// Read all of the dependent values. If any of them have changed since last
// time, then we'll want to recompute our output.
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keys.forEach((key) => {
const value = typeof this[key] === 'function' ? this[key]() : this[key];
if (dependentValues[key] !== value) {
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recompute = true;
dependentValues[key] = value;
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}
});
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if (recompute) {
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computedValue = compute.apply(
this,
keys.map((key) => dependentValues[key])
);
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}
return computedValue;
};
}