javascript - Smooth scrolling not so smooth -


i have been trying create smooth scrolling plain js. tried typical animation timing using this:

function animate(x) {     var start = new date();     var id = setinterval(function () {         var timepassed = new date() - start;         var progress = timepassed / x.duration;         if (progress > 1) {             progress = 1;         }         var delta = x.delta(progress);         x.step(delta);         if (progress == 1) {             clearinterval(id);         }     }, x.delay); }

after i'm measuring offsettop elements , using scrollto() there using window.scrollto(0, delta * to.offsettop); delta returned progress of time. problem not seem smooth eyes. missing important information animation?

demo

(using else if find out way anmiation should go - @ least now)

there 2 aspects issue here:

  • performance
  • perceived smoothness

performance

in code gain performance using requestanimationframe() instead of setinterval(). there nice article transitioning new method on mozilla or in-depth article paul irish. note: because want achieve 60fps, code shouldn't take longer 16ms calculation time.

perceived animation smoothness & easing

for second issue: animation linear, it's boring. when (if ever did) use animation-library or jquery animation, can specify timing-function animation should use. these example 'ease-in', 'ease-out', , on. can implement these in function through math. there many tools in web visualize these easing-equotations in different ways.

if hungry more input, check out robert penner's easing page.

last, not least, take @ this gist, provides javascript-implementation of different easing functions - oh , possible solution in vanilla js ;)

p.s. demonstration, your code little ease


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