29 lines
1008 B
JavaScript
29 lines
1008 B
JavaScript
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// -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
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/* exported parse */
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// parse:
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// @params: caller-provided parameter object, or %null
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// @defaults-provided defaults object
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// @allowExtras: whether or not to allow properties not in @default
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//
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// Examines @params and fills in default values from @defaults for
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// any properties in @defaults 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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// Return value: a new object, containing the merged parameters from
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// @params and @defaults
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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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