What is more effective: Implementing the LOOP before the CONDITIONAL or the CONDITIONAL before the LOOP in a menu-oriented code

Question

What is more effective: Implementing the LOOP before the CONDITIONAL or the CONDITIONAL before the LOOP in a menu-oriented code

Hello there, I have a code that applies photo effects from a menu, and I'm looking for some guidance on how to optimize it.

Should I organize my code with the LOOP before CONDITIONAL, like shown below:

function applyFilter(filter){
  var ctx = canvas.getContext('2d');
  var imageData = ctx.getImageData(img.x,img.y,img.width,img.height); 
  var dataArr = imageData.data;

  for(i = 0; i < dataArr.length; i+= 4){
    let color = {
      r : dataArr[i],
      g : dataArr[i+1],
      b : dataArr[i+2],
    }

    if(filter == "negative")
        negateImage(dataArr, i, color)
    else if(filter == "sephia")
        addSephia(dataArr, i, color)
    // else if  some other effects

or should I place the CONDITIONAL before the LOOP as seen in the example below:

function applyFilter(filter){

   if(filter == "negative")
       negateImage()
   else if(filter == "sephia")
      addSephia()
   // else if some other effects

}

function negateImage(){
  var ctx = canvas.getContext('2d');
  var imageData = ctx.getImageData(img.x,img.y,img.width,img.height); 
  var dataArr = imageData.data;

  for(i = 0; i < dataArr.length; i+= 4){
  // negate image algorithm
  }

}

Thanks in advance for your help!

javascript performance

Answer 1

Answer №1

Optimizing code by checking the condition only once can lead to better performance. Although the performance impact may be minimal, especially with branch prediction optimization, it is still important to prioritize readability and maintainability over premature optimization. It is advisable to conduct performance tests before identifying specific sections of code that require faster execution.

One approach could be to create a separate function for calling the negateImage or addSephia methods outside of the loop. Additionally, storing the length of the dataArr array instead of recalculating it in each iteration might improve efficiency:

function applyFilter(filter) {
  var ctx = canvas.getContext('2d');
  var imageData = ctx.getImageData(img.x, img.y, img.width, img.height);
  var dataArr = imageData.data;
  const fn = filter === 'negative' ?
    (i, color) => negateImage(dataArr, i, color) :
    (i, color) => addSephia(dataArr, i, color);
  const { length } = dataArr;
  for (let i = 0; i < length; i += 4) {
    fn(
      i,
      {
        r: dataArr[i],
        g: dataArr[i + 1],
        b: dataArr[i + 2],
      }
    );
    // ...

(Remember to declare the variable i within the for loop to avoid creating global variables implicitly.)

Answer 2

Optimizing code by checking the condition only once can lead to better performance. Although the performance impact may be minimal, especially with branch prediction optimization, it is still important to prioritize readability and maintainability over premature optimization. It is advisable to conduct performance tests before identifying specific sections of code that require faster execution.

One approach could be to create a separate function for calling the negateImage or addSephia methods outside of the loop. Additionally, storing the length of the dataArr array instead of recalculating it in each iteration might improve efficiency:

function applyFilter(filter) {
  var ctx = canvas.getContext('2d');
  var imageData = ctx.getImageData(img.x, img.y, img.width, img.height);
  var dataArr = imageData.data;
  const fn = filter === 'negative' ?
    (i, color) => negateImage(dataArr, i, color) :
    (i, color) => addSephia(dataArr, i, color);
  const { length } = dataArr;
  for (let i = 0; i < length; i += 4) {
    fn(
      i,
      {
        r: dataArr[i],
        g: dataArr[i + 1],
        b: dataArr[i + 2],
      }
    );
    // ...

(Remember to declare the variable i within the for loop to avoid creating global variables implicitly.)

What is more effective: Implementing the LOOP before the CONDITIONAL or the CONDITIONAL before the LOOP in a menu-oriented code

Answer №1

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