61 lines
2.3 KiB
JavaScript
61 lines
2.3 KiB
JavaScript
/***
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Copyright 2013 Teun Duynstee
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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module.exports = (function() {
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function identity(v){return v;}
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function ignoreCase(v){return typeof(v)==="string" ? v.toLowerCase() : v;}
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function makeCompareFunction(f, opt){
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opt = typeof(opt)==="object" ? opt : {direction:opt};
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if(typeof(f)!="function"){
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var prop = f;
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// make unary function
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f = function(v1){return !!v1[prop] ? v1[prop] : "";}
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}
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if(f.length === 1) {
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// f is a unary function mapping a single item to its sort score
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var uf = f;
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var preprocess = opt.ignoreCase?ignoreCase:identity;
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var cmp = opt.cmp || function(v1,v2) {return v1 < v2 ? -1 : v1 > v2 ? 1 : 0;}
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f = function(v1,v2) {return cmp(preprocess(uf(v1)), preprocess(uf(v2)));}
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}
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const descTokens = {"-1":'', desc:''};
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if(opt.direction in descTokens) return function(v1,v2){return -f(v1,v2)};
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return f;
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}
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/* adds a secondary compare function to the target function (`this` context)
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which is applied in case the first one returns 0 (equal)
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returns a new compare function, which has a `thenBy` method as well */
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function tb(func, opt) {
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/* should get value false for the first call. This can be done by calling the
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exported function, or the firstBy property on it (for es6 module compatibility)
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*/
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var x = (typeof(this) == "function" && !this.firstBy) ? this : false;
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var y = makeCompareFunction(func, opt);
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var f = x ? function(a, b) {
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return x(a,b) || y(a,b);
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}
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: y;
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f.thenBy = tb;
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return f;
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}
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tb.firstBy = tb;
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return tb;
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})();
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