How to round an output step .5 (javascript) and calculate with the output?

Question

I am not very familiar with JavaScript and/or form calculations. The form and script I made after searching the internet about the topic.

How can I round the output (output_abc) in 0.5 steps (1.0 1.5 2.0 … 7.7=7.5 or 7.8=8.0) and where to place it? How can I (after rounding the output) [input_a] + [output_abc]?

I am open to all suggestions, pointing directions, help.

 (function() { function calcABC(input_a, input_b, input_c) { input_a = parseFloat(input_a); input_b = parseFloat(input_b); input_c = parseFloat(input_c); return (input_a + input_b + input_c).toFixed(1); } var SUM_ABC = document.getElementById("FORMINPUT"); if (SUM_ABC) { SUM_ABC.onsubmit = function() { this.output_abc.value = calcABC(this.input_a.value, this.input_b.value, this.input_c.value); return false; }; } }()); 

 <form id="FORMINPUT" action=""> <p><label for="input_a">input a</label> <input id="input_a" name="input_a" type="number" pattern="[1-9]" min="1" max="99" /></p> <p><label for="input_b">input b</label> <input id="input_b" name="input_b" type="number" pattern="[1-9]" min="1" max="99" /></p> <p><label for="input_c">input c</label> <input id="input_c" name="input_c" type="number" pattern="[1-9]" min="1" max="99" /></p> <p><input type="reset" value="Reset" /> <input type="submit" value="Calculate" /></p> <p><label for="output_abc">output abc</label> <output id="output abc" name="output abc" type="number"></output> </p> <p>Here I want to display [input_a + output_abc]</p> </form> 

Answer 1

What you can do is round your ouput_abc as

Math.round(output.abc * 2)/2

It will give you the output in 0.5 steps

Answer 2

Rounding to 0.5, is very similar to rounding say to 2 decimal places etc.

Basically multiple by X, round, and then divide by X..

X = to the rounding spec. So if you wanted to round to 1 decimal place for example -> 7.17 = Math.round(7.17 * 10) / 10 , this would of course give you 7.2

So to round by 0.5 , X will just equal 2..

eg.

Math.round(7.7 * 2) / 2 === 7.5

Answer 3

Maybe you can add after the line where you are calling the calcABC function but before that assign the return value from the function to a variable.

  function calcABC(input_a, input_b, input_c) {
    input_a = parseFloat(input_a);
    input_b = parseFloat(input_b);
    input_c = parseFloat(input_c);
    return (input_a + input_b + input_c).toFixed(1);
  }
  var SUM_ABC = document.getElementById("FORMINPUT");
  if (SUM_ABC) {
    SUM_ABC.onsubmit = function() {
      var outputValue = calcABC(this.input_a.value, this.input_b.value, this.input_c.value);
this.output_abc.value = Math.round(outputValue * 2)/2
      return false;
    };
  }
}());````