I have several arrays like:
var arr1 = ['A', 'B', 'C', 'D'],
arr2 = ['A', 'C', 'D'],
arr3 = ['B', 'D'];
I now want them being sorted by a custom pattern, e.g. ['D', 'C', 'A', 'B']. I am using lodash and looking for a smart way of doing this.
You can use an object to efficiently map values to sortable values:
var arr1 = [ "A", "B", "C", "D" ];
var map = { D: 1, C: 2, A: 3, B: 4 };
arr1.sort(function(x, y){ return map[x] - map[y]; });
// show result in snippet
document.write(JSON.stringify(arr1));The same basic idea as Guffa's solution, but with a reusable API:
var makeSorter = function(pattern) {
var map = _.mapValues(_.invert(pattern), Number);
return function(vals) {
return vals.sort(function(a, b) {
return map[a] - map[b];
});
};
};
var mySorter = makeSorter(['D', 'C', 'A', 'B']);
mySorter(['A', 'B', 'C', 'D']); //=> ["D", "C", "A", "B"]
mySorter(['A', 'C', 'D']); //=> ["D", "C", "A"]
If there might be values in your data not in your pattern, then you might need something slightly more complex:
var makeSorter = function(pattern) {
var map = _.mapValues(_.invert(pattern), function(s) {return Number(s) + 1;});
return function(vals) {
return vals.sort(function(a, b) {
return (map[a] || Infinity) - (map[b] || Infinity);
});
};
};
mySorter(['A', 'X', 'B', 'C', 'Q']); //=> ["C", "A", "B", "X", "Q"]
Also, how nice ES6 arrow functions are. This is the equivalent of the first version, in ES6:
var makeSorter = pattern => {
let map = _.mapValues(_.invert(pattern), Number);
return vals => vals.sort((a, b) => map[a] - map[b]);
};
var pattern = ['D', 'C', 'A', 'B'];
function sortArray (array, pattern) {
return array.sort(function (a, b) {
if (pattern.indexOf(a) === pattern.indexOf(b)) {
return 0;
} else {
return pattern.indexOf(a) > pattern.indexOf(b) ? 1 : -1;
}
});
}
// use like:
var sortedArray = sortArray(['A', 'C', 'D'], pattern);
