settimeout-setinterval.js

function f1() {
  var count = 1;
  var last = Date.now();
  var ret = [];
  setTimeout(function() {
    ret.push( Date.now() - last );
    var i = 0, c;
    while ( i++ < 100000 ) {
      c = document.getElementsByTagName( 'a' );
    }
    if ( count++ > 100 ) {
      console.log( ret );
      return;
    }
    else {
      last = Date.now();
      setTimeout( arguments.callee, 10 );
    }
  }, 10);
}

function f2() {
  var count = 1;
  var last = Date.now();
  var ret = [];
  var inter = setInterval(function() {
    ret.push( Date.now() - last );
    var i = 0, c;
    while ( i++ < 100000 ) {
      c = document.getElementsByTagName( 'a' );
    }
    if ( count++ > 100 ) {
      clearInterval( inter );
      console.log( ret );
    }
    else last = Date.now();
  }, 10);
}


// 10s 时间内执行了多少次.
function f3() {
  var time = 10 * 1000; // 10s
  var last = Date.now();
  var count = 0;
  setTimeout(function() {
    if ( Date.now() - last > time ) {
      console.log( 'f3:', count );
      return;
    }
    count++;
    var i = 0, c;
    while ( i++ < 100000 ) {
      c = document.getElementsByTagName( 'a' );
    }
    setTimeout( arguments.callee, 10 );
  }, 10);
}

function f4() {
  var count = 0;
  var time = 10 * 1000;
  var last = Date.now();
  var inter = setInterval(function() {
    if ( Date.now() - last > time ) {
      clearInterval( inter );
      console.log( 'f4: ', count );
      return;
    }
    count++;
    var i = 0, c;
    while ( i++ < 100000 ) {
      c = document.getElementsByTagName( 'a' );
    }
  }, 10);
}


f1();
f2();
f3();
f4();