Develop Reference

Fastest way to convert a string into a Float32Array

How can I convert a string containing floats written out (not stored as JSON or something like that) into a Float32Array? I tried this but it doesn't work:
var str = "2.3 4.3 3.145";
var arr1 = parseFloat(str);
var arr2 = new Float32Array(arr1);

You have to split the values up, and then you can use Float32Array.from with the mapping callback:
const arr = Float32Array.from(str.split(" "), parseFloat);
const str = "2.3 4.3 3.145";
const arr = Float32Array.from(str.split(" "), parseFloat);
console.log(arr);
Note: Unlike parseInt, it's safe to use parseFloat the way it's used above, it ignores all but its first argument so it doesn't care that it gets called with more than one argument by from. If you had to do something like this to create (say) a Uint8Array, you couldn't use parseInt as above because it would be confused by the second argument it would receive. In that case, an arrow function is a simple way to fix it (and lets you be specific about the number base as well):
const arr = Uint8Array.from(str.split(" "), n => parseInt(n, 10));

You can split, then map to an array of floats
const str = "2.3 4.3 3.145";
const arr1 = str.split(' ').map(parseFloat);
const arr2 = new Float32Array(arr1);
console.log(arr1);
console.log(arr2);

Javascript - How to split a string into a nested array?

I know I can use split function to transform a string to an array but how can a string be split twice to produce a nested array?
I expected this would be sufficent but it does not produce the desired output.
var myString = "A,B,C,D|1,2,3,4|w,x,y,z|"
var item = myString.split("|");
var array = [item.split(",")];
Would it be more optimal to use a for each loop?
EXPECTED OUTPUT
var array = [
["A","B","C","D"],
["1","2","3","4"],
["w","x","y","z"],
];

Once you've split on |, use .map to account for the nesting before calling .split again. There's also an empty space after the last |, so to exclude that, filter by Boolean first:
const myString = "A,B,C,D|1,2,3,4|w,x,y,z|";
const arr = myString
.split('|')
.filter(Boolean)
.map(substr => substr.split(','));
console.log(arr);
Or you could use a regular expression to match anything but a |:
const myString = "A,B,C,D|1,2,3,4|w,x,y,z|";
const arr = myString
.match(/[^|]+/g)
.map(substr => substr.split(','));
console.log(arr);

var myString = "A,B,C,D|1,2,3,4|w,x,y,z"
var item = myString.split("|");
var outputArr = item.map(elem => elem.split(","));
console.log(outputArr);

Array values to a string in loop

I have an object (key value pair) looks like this
I want to get a string of '[100000025]/[100000013]'
I can't use var str = OBJ[0].PC + OBJ[1].PC (which gives me '100000025100000013')
because I need the bracket structure.
The number of items can vary.
Added >> Can it be done without using arrow function?

const string = array.map(({PC}) => `[${PC}]`).join('/')
You could map every string to the string wrapped in brackets, then join that by slashes.

You can use a map() and a join() to get that structure. - this is hte same solution as Puwka's = but without the template literal.
var data = [
{am: 1, ct: "", pc: "1000000025"},
{am: 2, ct: "", pc: "1000000013"}
];
let newArr = data.map(item => "[" + item.pc +"]");
console.log(newArr.join("/")); // gives [1000000025]/[1000000013]

You can always use classic for in loop
let arr = [{PC:'1000'},{PC:'10000'}]
let arrOut = [];
for(let i = 0; i < arr.length; i++) {
arrOut.push('[' + arr[i].PC + ']');
}
now the arrOut is equal ["[1000]", "[10000]"] what we need is to convert it to a string and add '/' between items.
let str = arrOut.join('/');
console.log(str) // "[1000]/[10000]"

So you need a string in the format of: xxxx/yyyyy from a complex object array.
const basedata = [...];
const result = basedata.map( item => `[${item.PC}]` ).join('/')
so i will explain it now. The map function will return a new array with 1 entry per item. I state that I want PC, but i added some flavor using ticks to inject it inbetween some brackets. At this point it looks like: ["[1000000025]","[100000013]"] and then join will join the arrays on a slash, so it will turn into an array.
"[100000025]/[100000013]"
Now, this will expand based on the items in your basedata. So if you have 3 items in your basedata array, it would return:
"[10000000025]/[100000013]/[10000888]"

First if you want to divide the result then it will be better to change it into number and then just do the division.
Example
Number.parseInt("100000025")/Number.parseInt("100000013")
If you want to display it then better to use string interpolation
surround it with back tick
[${[0].PC}]/[${[1].PC}]
Hope this is what are you looking for

javascript comma separated list to array

I have this type of list from javascript:
Amila,Asanka,Imaad,Kelum,Lakshan,Sagara,Thilina
I used the following code to convert to my output
var array = columnsload.split(",");
var string = JSON.stringify(columnsload);
var nameArray = string.split(',');
The output is like this :
"Amila,Asanka,Imaad,Kelum,Lakshan,Sagara,Thilina"
But I really need it like this :
["Amila","Asanka","Imaad","Kelum","Lakshan","Sagara","Thilina"]
Anyone know how to get output like this?

the split function is enough to convert the string into an array;
var names = "Amila,Asanka,Imaad,Kelum,Lakshan,Sagara,Thilina";
var nameArr = names.split(",");
console.log( nameArr );
http://www.w3schools.com/jsref/jsref_split.asp

Just do var nameArray = columnsload.split(',');. You dont need to stringify the array and then split it again, just one .split would be enough.
var columnsload = "Amila,Asanka,Imaad,Kelum,Lakshan,Sagara,Thilina";
var nameArray = columnsload.split(',');
console.log(nameArray);
If you need the whole thing to be string, you can run a JSON.stringify on the array after.
var columnsload = "Amila,Asanka,Imaad,Kelum,Lakshan,Sagara,Thilina";
var nameArray = columnsload.split(',');
console.log(JSON.stringify(nameArray));
// outputs ["Amila","Asanka","Imaad","Kelum","Lakshan","Sagara","Thilina"]
// as one string.

Elegant way to convert string of values into a Javascript array?

I have an ajax request that returns a list of values like this:
"1,2,3,4,5,6"
I need it to be a javascript array with numbers:
[1,2,3,4,5,6]
I tried:
var array = new Array("1,2,3,4,5,6".split(","))
But the numbers are still strings in the output:
["1","2","3","4","5","6"]
Is there a clean way to have it as a numbered array? Preferably without writing a function to iterate through it?

You need to loop through and convert them to numbers, like this:
var array = "1,2,3,4,5,6".split(",");
for(var i=0; i<array.length; i++) array[i] = +array[i];
Or, the more traditional example:
var array = "1,2,3,4,5,6".split(",");
for(var i=0; i<array.length; i++) array[i] = parseInt(array[i], 10);

A more jQuery-centric approach using jQuery.map():
var str = "1,2,3,4,5,6";
var arr = $.map(str.split(","), function(el) { return parseInt(el, 10); });

Not sure if this counts as writing a function but you can use the map function in jquery. I saw you listed as a tag so I assume you are using:
var stringArray = "1,2,3,4,5,6".split(",");
var numberArray = $.map(stringArray,
function(item, i)
{
return parseInt(item, 10);
});

// jquery must have a way to do what any modern browser can do:
var str= "1,2,3,4,5,6";
var arr= str.split(',').map(Number);
// returns an array of numbers

If you trust the ajax response, and if (for whatever reason) you're committed to not using a loop, you can always go with eval:
var str = "1,2,3,4,5,6";
var array = eval("[" + str + "]");

If you don't wish to expliclty iterate you can use array.map, javascripts map function.
array.map(callbackFunc, array);
var arr = array.map(function(x) {return parseInt(x);}, "1,2,3,4,5,6".split(","));
http://www.tutorialspoint.com/javascript/array_map.htm
Theres probably a better reference somewhere but I don't us javascript enough to have a good favorite reference site.
EDIT - i see jQuery has its own map, thats probably worth looking into.