Debounce a function when you want it to execute only once after a defined interval of time. If the event occurs multiple times within the interval, the interval is reset each time.
Example A user is typing into an input field and you want to execute a function, such as a call to the server, only when the user stops typing for a certain interval, such as 500ms.
{ | |
// http://eslint.org/docs/rules/ | |
"ecmaFeatures": { | |
"binaryLiterals": false, // enable binary literals | |
"blockBindings": false, // enable let and const (aka block bindings) | |
"defaultParams": false, // enable default function parameters | |
"forOf": false, // enable for-of loops | |
"generators": false, // enable generators | |
"objectLiteralComputedProperties": false, // enable computed object literal property names |
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.
elem.offsetLeft
,elem.offsetTop
,elem.offsetWidth
,elem.offsetHeight
,elem.offsetParent
In JavaScript, all binding declarations are instantiated when control flow enters the scope in which they appear. Legacy var and function declarations allow access to those bindings before the actual declaration, with a "value" of undefined
. That legacy behavior is known as "hoisting". let and const binding declarations are also instantiated when control flow enters the scope in which they appear, with access prevented until the actual declaration is reached; this is called the Temporal Dead Zone. The TDZ exists to prevent the sort of bugs that legacy hoisting can create.