2015-07-15 12:30:11 +08:00
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/**
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* The `computed` utility creates a function that will cache its output until
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* any of the dependent values are dirty.
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*
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* @param {...String} dependentKeys The keys of the dependent values.
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* @param {function} compute The function which computes the value using the
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* dependent values.
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2015-08-26 15:41:54 +08:00
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* @return {Function}
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2015-07-15 12:30:11 +08:00
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*/
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export default function computed(...dependentKeys) {
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const keys = dependentKeys.slice(0, -1);
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const compute = dependentKeys.slice(-1)[0];
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const dependentValues = {};
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let computedValue;
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2015-04-25 20:58:39 +08:00
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2020-04-17 17:57:55 +08:00
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return function () {
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2015-07-15 12:30:11 +08:00
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let recompute = false;
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// Read all of the dependent values. If any of them have changed since last
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// time, then we'll want to recompute our output.
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2020-04-17 17:57:55 +08:00
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keys.forEach((key) => {
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2015-07-15 12:30:11 +08:00
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const value = typeof this[key] === 'function' ? this[key]() : this[key];
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if (dependentValues[key] !== value) {
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2015-04-25 20:58:39 +08:00
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recompute = true;
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2015-07-15 12:30:11 +08:00
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dependentValues[key] = value;
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2015-04-25 20:58:39 +08:00
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}
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2015-07-15 12:30:11 +08:00
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});
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2015-04-25 20:58:39 +08:00
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if (recompute) {
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2020-04-17 17:57:55 +08:00
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computedValue = compute.apply(
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this,
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keys.map((key) => dependentValues[key])
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);
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2015-04-25 20:58:39 +08:00
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}
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2015-07-15 12:30:11 +08:00
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return computedValue;
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};
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}
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