I want to sort a multidimensional array using the first row, I want that the second and the third row get the same sort order of the first row
Here is an example of array :
var arr =
[
[1,3,5,6,0,2],
[1,2,7,4,0,6],
[1,2,3,4,5,6]
]
the result that I want =
[
[0,1,2,3,5,6],
[0,1,6,2,7,4],
[5,1,6,2,3,4]
]
I tried the following function but it doesnt work as I want
arr = arr.sort(function(a,b) {
return a[0] > b[0];
});
What's wrong with my function ? Thank you
I think I understand what you're looking for:
a = [
[1,3,5,6,0,2],
[1,2,7,4,0,6],
[1,2,3,4,5,6]
]
transpose = m => m[0].map((_, c) => m.map(r => r[c]));
z = transpose(transpose(a).sort((x, y) => x[0] - y[0]))
z.map(r =>
document.write('<pre>'+JSON.stringify(r) + '</pre>'));In ES5
transpose = function(m) {
return m[0].map(function (_, c) {
return m.map(function (r) {
return r[c]
})
})
};
z = transpose(transpose(a).sort(function (x, y) { return x[0] - y[0] }));
UPD: the transpose trick is kinda "smart", but hardly efficient, if your matrices are big, here's a faster way:
a = [
[1,3,5,6,0,2],
[1,2,7,4,0,6],
[1,2,3,4,5,6]
]
t = a[0].map((e, i) => [e, i]).sort((x, y) => x[0] - y[0]);
z = a.map(r => t.map(x => r[x[1]]));
z.map(r =>
document.write('<pre>'+JSON.stringify(r) + '</pre>'));Basically, sort the first row and remember indexes, then for each row, pick values by an index.
functions.A bit more verbose than previous answer in ES5
var arr = [
[1, 3, 5, 6, 0, 2],
[1, 2, 7, 4, 0, 6],
[1, 2, 3, 4, 5, 6]
]
var sortIndices = arr[0].slice().sort(function(a, b) {
return a - b;
}).map(function(el) {
return arr[0].indexOf(el)
});
arr = arr.reduce(function(a, c) {
var sorted = sortIndices.map(function(i) {
return c[i];
});
a.push(sorted);
return a;
}, []);
document.getElementById('pre').innerHTML = JSON.stringify(arr)<pre id="pre"></pre>
.sortshould return a number, not a bool.