Develop Reference

How to force an integer into two digits exactly in JavaScript?

The problem is from my trying to convert number into a time format. I'd like to put time like "8:5" into "08:05". Any elegant JavaScript code?

Use split, map, slice and join
"8:5".split(":").map((s)=>("0"+s).slice(-2)).join(":"); //prints 08:05
You can invoke this at the blur/change event of your input box.

How to "unformat" a numerical string? JavaScript

So I know how to format a string or integer like 2000 to 2K, but how do I reverse it?
I want to do something like:
var string = "$2K".replace("/* K with 000 and remove $ symbol in front of 2 */");
How do I start? I am not very good regular expressions, but I have been taking some more time out to learn them. If you can help, I certainly appreciate it. Is it possible to do the same thing for M for millions (adding 000000 at the end) or B for billions (adding 000000000 at the end)?

var string = "$2K".replace(/\$(\d+)K/, "$1000");
will give output as
2000

I'm going to take a different approach to this, as the best way to do this is to change your app to not lose the original numeric information. I recognize that this isn't always possible (for example, if you're scraping formatted values...), but it could be useful way to think about it for other users with similar question.
Instead of just storing the numeric values or the display values (and then trying to convert back to the numeric values later on), try to update your app to store both in the same object:
var value = {numeric: 2000, display: '2K'}
console.log(value.numeric); // 2000
console.log(value.display); // 2K
The example here is a bit simplified, but if you pass around your values like this, you don't need to convert back in the first place. It also allows you to have your formatted values change based on locale, currency, or rounding, and you don't lose the precision of your original values.

Trouble converting javascript string to number

I have a script assigns a variable using parseFloat as follows:
var vendorCost = parseFloat(vendorSearchresults[0].getValue('vendorcost')).toFixed(2);
I assumed this would make the variable a number. However when I check it with typeof - it reports it as a string. My solution is as follows:
vendorCost = parseFloat(vendorCost);
Which works, however I'm trying to be more efficient when coding and would like to understand why it doesn't make vendorCost a number when assigning it a number? Is there a way I could make the first statement make vendorCost a number without the need for the second statement? Thanks in advance.
Update - just thought I should mention I'm having the exact same issue without using .toFixed -
var vendorLandedCost = parseFloat(vendorSearchresults[0].getValue('custentity_asg_landed_cost','vendor'));
vendorLandedCost = parseFloat(vendorLandedCost);

The last toFixed() call converts the result of the first parseFloat into a string.
Looks like you need to round the number to two decimal places, which is why you're using the parseFloat call. You can do something like this instead:
vendor_cost = Math.round(parseFloat(vendorSearchresults[0].getValue('vendorcost')) * 100) / 100

Well, Number.toFixed returns string because it is a data presentation function.
See the docs.

d3.format wont keep trailing zero

I'm using d3.round(num,2) to round a number from say, 2.567 to 2.57. My problem is that when I do this, I want 2 decimal numbers of precision to be used at all times/regardless of if it is a zero.
when I have a number like 2.201, I want the display to be 2.20, and instead am coming up with 2.2. Is there any way to format the round function to always include zeroes?
Thanks for any help!
Edit: used num.toFixed(2) and that works, but I am returning d3.format("$")(num.toFixed(2)) and that is only returning $2.3, which is the reason I needed this, I am looking to display a price. If anyone has help to offer with that, it would be great, thank you

Try this:
d3.format("$.3n")(num);

Parse json in javascript - long numbers get rounded

I need to parse a json that contains a long number (that was produces in a java servlet). The problem is the long number gets rounded.
When this code is executed:
var s = '{"x":6855337641038665531}';
var obj = JSON.parse(s);
alert (obj.x);
the output is:
6855337641038666000
see an example here: http://jsfiddle.net/huqUh/
why is that, and how can I solve it?

As others have stated, this is because the number is too big. However, you can work around this limitation by sending the number as a string like so:
var s = '{"x":"6855337641038665531"}';
Then instead of using JSON.parse(), you can use a library such as javascript-bignum to work with the number.

It's too big of a number. JavaScript uses double-precision floats for numbers, and they have about 15 digits of precision (in base 10). The highest integer that JavaScript can reliably save is something like 251.
The solution is to use reasonable numbers. There is no real way to handle such large numbers.

The largest number JavaScript can handle without loss of precision is 9007199254740992.

I faced this issue some time ago, I was able to solve using this lib: https://github.com/josdejong/lossless-json
You can check this example:
let text = '{"normal":2.3,"long":123456789012345678901,"big":2.3e+500}';
// JSON.parse will lose some digits and a whole number:
console.log(JSON.stringify(JSON.parse(text)));
// '{"normal":2.3,"long":123456789012345680000,"big":null}' WHOOPS!!!
// LosslessJSON.parse will preserve big numbers:
console.log(LosslessJSON.stringify(LosslessJSON.parse(text)));
// '{"normal":2.3,"long":123456789012345678901,"big":2.3e+500}'