from green to red color depend on percentage

Question

I have a poll system and I want answers for this poll to be colored. For example: If it\'s 10% it would be red, if 40% it would be yellow and if 80% it would be green, so I

Answer 1

You can do this in a few lines of code (not including comments) without the need for any color maps.

function hsl_col_perc(percent, start, end) {
  var a = percent / 100,
      b = (end - start) * a,
      c = b + start;

  // Return a CSS HSL string
  return 'hsl('+c+', 100%, 50%)';
}
//Change the start and end values to reflect the hue map
//Refernece : http://www.ncl.ucar.edu/Applications/Images/colormap_6_3_lg.png

/*
Quick ref:
    0 – red
    60 – yellow
    120 – green
    180 – turquoise
    240 – blue
    300 – pink
    360 – red
*/      

Example: https://jsfiddle.net/x363g1yc/634/

No need for color maps (Unless it is a non-linear color change, which was not asked)

Warning: This is not compatible with IE8 or below. (Thanks Bernhard Fürst)

// Just used as a shortcut for below, completely optional
const red = 0,
  yellow = 60,
  green = 120,
  turquoise = 180,
  blue = 240,
  pink = 300;

function hsl_col_perc(percent, start, end) {
  var a = percent / 100,
    b = (end - start) * a,
    c = b + start;

  // Return a CSS HSL string
  return 'hsl(' + c + ', 100%, 50%)';
}

// Simple little animation
var percent = 0,
  progressDiv = document.getElementById('progress'),
  textDiv = document.getElementById('progress-text'),
  progressContainerDiv = document.getElementById('progress-container')

function step(timestamp) {
  percent = (percent < 100) ? percent + 0.5 : 0;

  // Play with me!
  let colour = hsl_col_perc(percent, red, green); //Red -> Green
  progressDiv.style.backgroundColor = colour;
  progressContainerDiv.style.borderColor = colour;
  progressDiv.style.width = percent + '%';
  textDiv.innerHTML = Math.floor(percent);
  window.requestAnimationFrame(step);
}

window.requestAnimationFrame(step);

#progress {
  width: 0%;
  white-space: nowrap;
  text-wrap: none;
  height: 50px;
}

#progress-container {
  border: solid 2px black;
  width: 200px;
}