31 lines
1.0 KiB
JavaScript
31 lines
1.0 KiB
JavaScript
// -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
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/**
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* parse:
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*
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* @param {*} params caller-provided parameter object, or %null
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* @param {*} defaults provided defaults object
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* @param {boolean} [allowExtras] whether or not to allow properties not in `default`
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*
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* @summary Examines `params` and fills in default values from `defaults` for
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* any properties in `default` that don't appear in `params`. If
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* `allowExtras` is not %true, it will throw an error if `params`
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* contains any properties that aren't in `defaults`.
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*
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* If `params` is %null, this returns the values from `defaults`.
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*
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* @returns a new object, containing the merged parameters from
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* `params` and `defaults`
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*/
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export function parse(params = {}, defaults, allowExtras) {
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if (!allowExtras) {
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for (let prop in params) {
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if (!(prop in defaults))
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throw new Error(`Unrecognized parameter "${prop}"`);
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}
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}
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let defaultsCopy = Object.assign({}, defaults);
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return Object.assign(defaultsCopy, params);
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}
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