JavaScript 语句参考

JavaScript 语句

在 HTML 中，JavaScript 语句是 "instructions" 到网络浏览器的 "executed"。

此语句告诉浏览器在 id="demo" 的 HTML 元素内写入 "Hello Dolly."：

document.getElementById("demo").innerHTML = "Hello Dolly.";

有关语句的教程，请阅读我们的JavaScript 语句教程。

JavaScript 语句通常以语句标识符识别要执行的 JavaScript 操作。

语句标识符是保留字，不能用作变量名（或任何其他名称）。

下表列出了所有 JavaScript 语句标识符：

Statement	Description
break	Exits a switch or a loop
class	Declares a class
const	Declares a variable with a constant value
continue	Breaks one iteration (in the loop) if a specified condition occurs, and continues with the next iteration in the loop
debugger	Stops the execution of JavaScript, and calls (if available) the debugging function
do ... while	Executes a block of statements and repeats the block while a condition is true
for	Loops through a block of code a number of times
for ... in	Loops through the properties of an object
for ... of	Loops through the values of an iterable object
function	Declares a function
if ... else ... else if	Marks a block of statements to be executed depending on a condition
let	Declares a variable
return	Stops the execution of a function and returns a value from that function
switch	Marks a block of statements to be executed depending on different cases
throw	Throws (generates) an error
try ... catch ... finally	Marks the block of statements to be executed when an error occurs in a try block, and implements error handling
var	Declares a variable
while	Marks a block of statements to be executed while a condition is true