What are javascript expressions?

Javascript expressions include: 1. Arithmetic expression; 2. String expression; 3. Main expression; 4. Array and object initializer expression; 5. Logical expression; 6. Left-hand expression Formula; 7. Property access expression; 8. Object creation expression; 9. Function definition expression; 10. Call expression, etc.

The operating environment of this article: Windows 7 system, javascript version 1.8.5, DELL G3 computer

What are the javascript expressions?

An expression is a unit of code that can be evaluated and resolved into a value. Expressions in JS can be divided into several categories.

• Arithmetic expression

• String expression

• Main expression

• Array and object initializer expressions

• Logical expression

• Left side expression

• Property access expression

• Object creation expression

• Function definition expression

• Calling expressions

• Arithmetic expressions

Under this category, take all expressions that evaluate to a number:

1 / 2 i++ i -= 2 i * 2

String expression

Expression that evaluates to a string:

'A ' + 'string'

Main expression

Under this category, variable reference, literal and constants:

2 0.02 'something' true false this //the current object undefined i //where i is a variable or a constant

There are also some language keywords:

function class function* //the generator function yield //the generator pauser/resumer yield* //delegate to another generator or iterator async function* //async function expression await //async function pause/resume/wait for completion /pattern/i //regex () // grouping

Array and object initializer expressions

[] //array literal {} //object literal [1,2,3] {a: 1, b: 2} {a: {b: 1}}

Logical expressions

Logical expressions Use logical operators and resolve to Boolean values:

a && b a || b !a

Left side expression

new //create an instance of a constructor super //calls the parent constructor ...obj //expression using the spread operator

Property access expression

object.property //reference a property (or method) of an object object[property] object['property']

Object creation expression

new object() new a(1) new MyRectangle('name', 2, {a: 4})

Function definition expression

function() {} function(a, b) { return a * b } (a, b) => a * b a => a * 2 () => { return 2 }

Calling expression

Syntax for calling a function or method

a.x(2) window.resize()

Recommended learning: "js basic tutorial"

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