Tutorial: Good practices

Converting numbers: always use parseInt(num, 10)

Convert "16" to number: http://jsperf.com/number-vs-parseint-vs-plus/26

Convert "16px" to number: http://jsperf.com/number-vs-parseint-vs-plus/25

Cascading configuration options: use prototype rather than $.extend

This technique cannot be applied everywhere, but is a great candidate for Handsontable cascading settings pattern (Constructor options -> columns -> cells -> cellProperties).

See more: http://jsperf.com/extending-settings

Custom functions can be faster than native (for example forEach)

According to tests ran at JSPerf, MDN shim of forEach can be up to 5 times faster than the native implementation.

See more: http://jsperf.com/native-vs-implmented-0/5

forEach and filter are MUCH slower than for

for can be 10 times faster than a forEach.

See more: http://jsperf.com/for-vs-foreach/49

call is faster than apply

See more: http://jsperf.com/function-calls-direct-vs-apply-vs-call-vs-bind/33

Emptying nodes: always prefer removeNode() over innerHTML = ''

See more: http://jsperf.com/jquery-html-vs-empty-vs-innerhtml/9

Search for ID or by tag: prefer getElementById or getElementsByTagName

Get first element using DOM (getElementsByTagName('span')[0] or firstChild)

Create text elements: createTextNode can be many times faster than innerHTML

Check if element has child nodes: if (DIV.firstChild)

Change style by caching var style = element.style

See more: http://jsperf.com/change-css-in-many-ways