67 lines
1.5 KiB
JavaScript
67 lines
1.5 KiB
JavaScript
'use strict'
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const defaultOpts = { async: false, right: false }
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exports.compose = function compose(opts, fns) {
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if (Array.isArray(opts)) {
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fns = opts.slice() // don't mutate passed array
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opts = defaultOpts
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} else if (typeof opts === 'object') {
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opts = Object.assign({}, defaultOpts, opts)
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if (Array.isArray(fns)) {
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fns = fns.slice() // don't mutate passed array
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} else {
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fns = Array.prototype.slice.call(arguments, 1)
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}
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} else {
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fns = Array.from(arguments)
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opts = defaultOpts
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}
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const n = fns.length
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if (n === 0) {
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throw new TypeError('at least one function must be passed')
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}
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for (let i = 0; i < n; ++i) {
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const entry = fns[i]
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if (Array.isArray(entry)) {
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const fn = entry[0]
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const args = entry.slice()
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args[0] = undefined
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fns[i] = function composeWithArgs(value) {
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args[0] = value
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try {
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return fn.apply(this, args)
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} finally {
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args[0] = undefined
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}
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}
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}
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}
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if (n === 1) {
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return fns[0]
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}
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if (opts.right) {
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fns.reverse()
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}
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return opts.async
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? async function () {
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let value = await fns[0].apply(this, arguments)
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for (let i = 1; i < n; ++i) {
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value = await fns[i].call(this, value)
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}
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return value
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}
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: function () {
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let value = fns[0].apply(this, arguments)
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for (let i = 1; i < n; ++i) {
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value = fns[i].call(this, value)
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}
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return value
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}
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}
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