JS Basic Review

Function and the cords

Note: The default value of manually passing undefined also takes effect

The difference between function declarations and function expressions

Function declaration

function sayHi(name) { console.log(name) }
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Functional expression

let sayHi = function sayHi(name) { console.log(name) }
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The difference between

Function declarations globally available function expressions are created only when the code executes to them and are called only after creationCopy the code

The UI interaction

Null-value merge operator (??)

Null-value merge operator (??) Is a logical operator that returns the right-hand operand if the left-hand operand is null or undefined, otherwise returns the left-hand operand. Are still a little difference, and | | see example (console Google browser does not support??

const a = 0 || 1  // a=1
const a = 0 ?? 1  // a=0

const a = '' || 1   // a=1
const a = '' ?? 1  // a=''
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