JS JavaScript: Conditions
A condition is an expression that evaluates whether something is true or false. Conditions are very much used. Usually the code should execute one way if the condition is true and another way if the condition is false.
JavaScript hoisting is basically that declarations are moved to the top of your code.
Actually your function and variable declarations are added to memory during the compile phase.
And they stay exactly where you typed them in your code.
JavaScript hoists all declarations
JavaScript hoists all declarations. Initializations are not hoisted.
Declare and initialize a variable, e.g. var x = 8;
, only the var x;
part (the declaration) is hoisted.
The x = 8;
(the initialization) is not hoisted.
A variable that is declared but not initialized is automatically set as undefined
.
Take a look at the examples to understand this.
Hoisting Variables Examples
// This is how you would expect to write the code var x = 8; // Initialize and assign 8 to x console.log('X has the value: '+ x); // The printed text is: "X has the value: 8" // Here y is assigned before it is declared y = 8; // Assign 8 to y console.log('Y has the value: '+ y); // The printed text is: "Y has the value: 8" var y; // Declare y
Hoisting Variables Undefined Examples
// Declare and assign the variable at the end // Only the declaration is hoisted console.log('Z has the value: '+ z); // The printed text is: "Z has the value: undefined" var z = 8; // Declare and assign 8 to z
Hoisting Functions Examples
// This is how you would expect to write the code function printName(name) { console.log("My name is " + name); } printName("Donald"); // The printed text is: "My name is Donald" // Here the function is called before it is declared printCity("London"); // The printed text is: "My favorite city is London" function printCity(name) { console.log("My favorite city is " + name); }
Let and Const Statement
Variables and constants declared with let
or const
are not hoisted!
Hoisting Best Practices
Hoisting is not well known to many developers.
It is considered a best practice to declare variables at the top of their respective scopes. Then you would limit undesirable effects.
Always initialize variables when they are declared. This will provide better code and avoid undefined
variables.
JavaScript strict mode gives an error if variables is used before they are declared.
A condition is an expression that evaluates whether something is true or false. Conditions are very much used. Usually the code should execute one way if the condition is true and another way if the condition is false.
Const is a keyword that indicates a constant. It describes an entity that cannot be changed at runtime. We cannot reassign a constant. With constants we lose the ability to modify variables at runtime and we gain run-time validation.
One of t....
Events are actions or occurrences that happen to HTML elements.
JavaScript can act when an HTML Event occurs.
Events can represent everything from basic user interactions to automated notifications of things happening in the rendering model.
JavaScript strings are used for storing and manipulating text.
A string can be any text inside double or single quotes.
Strings can contain letters, numbers, symbols, punctuation, and even emoji.
A JavaScript string stores a series of characters like "Jonny ....
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