I have an array of arrays like this:
myData = [
["name1", 34.1, 43.1, 55.2],
["name2", 5.3, 23.6, 40.9],
["name3", 43.5, 77.8, 22.4]
];
I want to get an array containing only the first element of each array like this: ["name1", "name2", "name3"].
I tried to do it like this but doesn't work:
var arrayTitle = myData.map(function(x) {
return [myData[x][0]];
});
Any suggestions?
You could return just the first elementn of x, an element of the outer array.
var myData = [["name1", 34.1, 43.1, 55.2], ["name2", 5.3, 23.6, 40.9], ["name3", 43.5, 77.8, 22.4]],
arrayTitle = myData.map(function(x) {
return x[0];
});
console.log(arrayTitle);Your x itself is an array. So you need not to touch myData again inside.
var arrayTitle = myData.map(function(x) {
return x[0];
});
or with a traditional loop
myData = [
["name1", 34.1, 43.1, 55.2],
["name2", 5.3, 23.6, 40.9],
["name3", 43.5, 77.8, 22.4]
];
var arrayTitle = [];
for(var k in myData)
arrayTitle.push(myData[k][0]);
console.log(arrayTitle);
for...in... is for objects
With your actual code return [myData[x][0]], you are returning undefined, because x is the iterated item, so it's an array and not an index.
And using the wrapping [] is useless here, it's a destructing syntax, we don't need it here.
You should only return item[0] in each iteration:
var res = myData.map(function(arr) {
return arr[0];
});
Demo:
myData = [
["name1", 34.1, 43.1, 55.2],
["name2", 5.3, 23.6, 40.9],
["name3", 43.5, 77.8, 22.4]
];
var res = myData.map(function(arr) {
return [arr[x][0]];
});
console.log(res);This could be the shortest answer:
var res = myData.map(a => a[0])
xis an element of the array and not an index. And don't wrap the return value in an array[]