jhonalino

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

jhonalino

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jhonalino

/* http://meyerweb.com/eric/tools/css/reset/ 
   v2.0 | 20110126
   License: none (public domain)
*/

html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,

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license: mit

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var val = undefined 

if(val === undefined || val === null) {
  //do something 
}

if(val == undefined) {
  //do something
}

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if(num === 10 || num === "10") {
  //do someting
}


if(num == 10) {
  //do someting
}

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function doImportantStuff() { 
  //function scope
  var someVariable = "important stuff"; 
}

{
  //block scope
  let anotherVariable = "not so important";
}

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function doImportantStuff() {
  var someVariable = "important stuff";
 
  console.log(someVariable); // "important stuff" 
  console.log(anotherVariable); // oops can't access that
}

function anotherImportantStuff() {
  var anotherVariable = "not so important";
}

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function doImportantStuff() {
  var someVariable = "important stuff";
  
  function reportImportantStuff() {
    console.log(someVariable) // "important stuff"
  }
  
  reportImportantStuff();
}

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Sans jQuery

Events

// jQuery
$(document).ready(function() {
  // code
})