Performance tunning

[dreamerhammer]

Optimize javascript

1 Debounce input handler

function onScroll (evt) {

  // Store the scroll value for laterz.
  lastScrollY = window.scrollY;

  // Prevent multiple rAF callbacks.
  if (scheduledAnimationFrame)
    return;

  scheduledAnimationFrame = true;
  requestAnimationFrame(readAndUpdatePage);
}
window.addEventListener('scroll', onScroll);

2 Use requestAnimationFrame to execute animation

3 Use requestAnimationFrame to break big task into micro tasks

function processTaskList(taskStartTime) {
  var taskFinishTime;

  do {
    // Assume the next task is pushed onto a stack.
    var nextTask = taskList.pop();

    // Process nextTask.
    processTask(nextTask);

    // Go again if there’s enough time to do the next task.
    taskFinishTime = window.performance.now();
  } while (taskFinishTime - taskStartTime < 3);

  if (taskList.length > 0)
    requestAnimationFrame(processTaskList);
}

Optimize style

1 Use simple style rules

2 Use BEM for css

3 Limit the amount of elements effected by css tunning

Optimize layout

1 Avoid setting width/height/position/float/display related

2 Use flexbox

3 Avoid force layout synchronization

Optimize Paint and Composition

1 Use transform and opacity

2 Reducing complex paint works, like box-shadow

3 Use will-change

.moving-element {
  will-change: transform;
}

4 Limit paint area, exp. not update header and footer together

Reference

https://developers.google.com/web/fundamentals/performance/rendering/

[dreamerhammer]

Worker

1. Embedded Worker

var textContent = `
    onmessage = function(oEvent){
        importScripts()
     }
`
var blob = new Blob([textContent], {type: 'text/javascript'})
var worker = new Worker(window.URL.createObjectURL(blob));
worker.postMessage("Hello2")