How to Force Js to Do Math Instead of Putting Two Strings Together

How to force JS to do math instead of putting two strings together

You have the line

dots = document.getElementById("txt").value;

in your file, this will set dots to be a string because the contents of txt is not restricted to a number.

to convert it to an int change the line to:

dots = parseInt(document.getElementById("txt").value, 10);

Note: The 10 here specifies decimal (base-10). Without this some browsers may not interpret the string correctly. See MDN: parseInt.

Javascript (+) sign concatenates instead of giving sum of variables

Use this instead:

var divID = "question-" + (i+1)

It's a fairly common problem and doesn't just happen in JavaScript. The idea is that + can represent both concatenation and addition.

Since the + operator will be handled left-to-right the decisions in your code look like this:

• "question-" + i: since "question-" is a string, we'll do concatenation, resulting in "question-1"
• "question-1" + 1: since "queston-1" is a string, we'll do concatenation, resulting in "question-11".

With "question-" + (i+1) it's different:

• since the (i+1) is in parenthesis, its value must be calculated before the first + can be applied:
  
  
  • i is numeric, 1 is numeric, so we'll do addition, resulting in 2
• "question-" + 2: since "question-" is a string, we'll do concatenation, resulting in "question-2".

Adding two numbers concatenates them instead of calculating the sum

They are actually strings, not numbers. The easiest way to produce a number from a string is to prepend it with +:

var x = +y + +z;

javascript (+) sign concatenates instead of giving sum?

Here value gives you a string, hence the concatenation. Try parsing it as an Number instead:

var sum = parseInt(numberOne) + parseInt(numberTwo);

See the demo fiddle.

How to add two strings as if they were numbers?

I would use the unary plus operator to convert them to numbers first.

+num1 + +num2;

This is adding 2 strings when i am trying to add to intergers?

You need to use parseInt on no1 and no2 like follows:

  var noO = prompt("please enter a number:");

  var noT = prompt("please enter a second number:");

  var no1 = noO;

  var no2 = noT;

  var res = parseInt(no1, 10) + parseInt(no2, 10);

  alert("the adiition of thoes 2 numbers is: " + res);

Prompts when numbers are added together it just puts the number and the other number together

Common issue; it is reading 55 as a string, rather than a number, do:

sumAngle = parseInt(angle1, 10) + parseInt(angle2, 10);

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