JavaScript 语法6335

javaScript 语法

JavaScript 是一个程序语言。语法规则定义了语言结构。

JavaScript 语法

JavaScript 是一个脚本语言。

它是一个轻量级，但功能强大的编程语言。

JavaScript 字面量

在编程语言中，一般固定值称为字面量，如 3.14。

数字（Number）字面量 可以是整数或者是小数，或者是科学计数(e)。

3.14 1001 123e5

https://avg.163.com/topic/detail/12447488 https://avg.163.com/topic/detail/12447486 https://avg.163.com/topic/detail/12447487 https://avg.163.com/topic/detail/12447485 https://avg.163.com/topic/detail/12447484 https://avg.163.com/topic/detail/12447483 https://avg.163.com/topic/detail/12447481 https://avg.163.com/topic/detail/12447482 https://avg.163.com/topic/detail/12447474 https://avg.163.com/topic/detail/12447480 https://avg.163.com/topic/detail/12447476 https://avg.163.com/topic/detail/12447479 https://avg.163.com/topic/detail/12447478 https://avg.163.com/topic/detail/12447477 https://avg.163.com/topic/detail/12447475 https://avg.163.com/topic/detail/12447467 https://avg.163.com/topic/detail/12447473 https://avg.163.com/topic/detail/12447472 https://avg.163.com/topic/detail/12447471 https://avg.163.com/topic/detail/12447470 https://avg.163.com/topic/detail/12447468 https://avg.163.com/topic/detail/12447469 https://avg.163.com/topic/detail/12447464 https://avg.163.com/topic/detail/12447466 https://avg.163.com/topic/detail/12447465 https://avg.163.com/topic/detail/12447463 https://avg.163.com/topic/detail/12447462 https://avg.163.com/topic/detail/12447459 https://avg.163.com/topic/detail/12447461 https://avg.163.com/topic/detail/12447460 https://avg.163.com/topic/detail/12447457 https://avg.163.com/topic/detail/12447458 https://avg.163.com/topic/detail/12447456 https://avg.163.com/topic/detail/12447455 https://avg.163.com/topic/detail/12447454 https://avg.163.com/topic/detail/12447453 https://avg.163.com/topic/detail/12447452 https://avg.163.com/topic/detail/12447451 https://avg.163.com/topic/detail/12447450 https://avg.163.com/topic/detail/12447446 https://avg.163.com/topic/detail/12447449 https://avg.163.com/topic/detail/12447448 https://avg.163.com/topic/detail/12447447 https://avg.163.com/topic/detail/12447445 https://avg.163.com/topic/detail/12447442 https://avg.163.com/topic/detail/12447444 https://avg.163.com/topic/detail/12447438 https://avg.163.com/topic/detail/12447443 https://avg.163.com/topic/detail/12447441 https://avg.163.com/topic/detail/12447440 https://avg.163.com/topic/detail/12447439 https://avg.163.com/topic/detail/12447435 https://avg.163.com/topic/detail/12447437 https://avg.163.com/topic/detail/12447436 https://avg.163.com/topic/detail/12447434 https://avg.163.com/topic/detail/12447433 https://avg.163.com/topic/detail/12447432 https://avg.163.com/topic/detail/12447431 https://avg.163.com/topic/detail/12447430 https://avg.163.com/topic/detail/12447429 https://avg.163.com/topic/detail/12447428 https://avg.163.com/topic/detail/12447427 https://avg.163.com/topic/detail/12447423 https://avg.163.com/topic/detail/12447425 https://avg.163.com/topic/detail/12447426 https://avg.163.com/topic/detail/12447424 https://avg.163.com/topic/detail/12447422 https://avg.163.com/topic/detail/12447421 https://avg.163.com/topic/detail/12447418 https://avg.163.com/topic/detail/12447420 https://avg.163.com/topic/detail/12447419 https://avg.163.com/topic/detail/12447417 https://avg.163.com/topic/detail/12447415 https://avg.163.com/topic/detail/12447414 https://avg.163.com/topic/detail/12447408 https://avg.163.com/topic/detail/12447413 https://avg.163.com/topic/detail/12447410 https://avg.163.com/topic/detail/12447412 https://avg.163.com/topic/detail/12447411 https://avg.163.com/topic/detail/12447409 https://avg.163.com/topic/detail/12447407 https://avg.163.com/topic/detail/12447406 https://avg.163.com/topic/detail/12447405 https://avg.163.com/topic/detail/12447404 https://avg.163.com/topic/detail/12447403 https://avg.163.com/topic/detail/12447402 https://avg.163.com/topic/detail/12447401 https://avg.163.com/topic/detail/12447399 https://avg.163.com/topic/detail/12447400 https://avg.163.com/topic/detail/12447398 https://avg.163.com/topic/detail/12447392 https://avg.163.com/topic/detail/12447397 https://avg.163.com/topic/detail/12447396 https://avg.163.com/topic/detail/12447394 https://avg.163.com/topic/detail/12447395 https://avg.163.com/topic/detail/12447393 https://avg.163.com/topic/detail/12447390 https://avg.163.com/topic/detail/12447391 https://avg.163.com/topic/detail/12447387 https://avg.163.com/topic/detail/12447389 https://avg.163.com/topic/detail/12447388 https://avg.163.com/topic/detail/12447386 https://avg.163.com/topic/detail/12447383 https://avg.163.com/topic/detail/12447372 https://avg.163.com/topic/detail/12439616 https://avg.163.com/topic/detail/12447384 https://avg.163.com/topic/detail/12439645 https://avg.163.com/topic/detail/12439654 https://avg.163.com/topic/detail/12439622 https://avg.163.com/topic/detail/12447376 https://avg.163.com/topic/detail/12447379 https://avg.163.com/topic/detail/12447374 https://avg.163.com/topic/detail/12447371 https://avg.163.com/topic/detail/12447373 https://avg.163.com/topic/detail/12447377 https://avg.163.com/topic/detail/12447375 https://avg.163.com/topic/detail/12447370 https://avg.163.com/topic/detail/12447369 https://avg.163.com/topic/detail/12447368 https://avg.163.com/topic/detail/12447367 https://avg.163.com/topic/detail/12447365 https://avg.163.com/topic/detail/12447364 https://avg.163.com/topic/detail/12447363 https://avg.163.com/topic/detail/12447362 https://avg.163.com/topic/detail/12447361 https://avg.163.com/topic/detail/12447360 https://avg.163.com/topic/detail/12447359 https://avg.163.com/topic/detail/12447357 https://avg.163.com/topic/detail/12447355 https://avg.163.com/topic/detail/12447358 https://avg.163.com/topic/detail/12447354 https://avg.163.com/topic/detail/12447353 https://avg.163.com/topic/detail/12447352 https://avg.163.com/topic/detail/12447351 https://avg.163.com/topic/detail/12447349 https://avg.163.com/topic/detail/12447350 https://avg.163.com/topic/detail/12447348 https://avg.163.com/topic/detail/12447347 https://avg.163.com/topic/detail/12447346 https://avg.163.com/topic/detail/12447345 https://avg.163.com/topic/detail/12447344 https://avg.163.com/topic/detail/12447343 https://avg.163.com/topic/detail/12447342 https://avg.163.com/topic/detail/12447341 https://avg.163.com/topic/detail/12447339 https://avg.163.com/topic/detail/12447338 https://avg.163.com/topic/detail/12447337 https://avg.163.com/topic/detail/12447336 https://avg.163.com/topic/detail/12447335 https://avg.163.com/topic/detail/12447334 https://avg.163.com/topic/detail/12447333 https://avg.163.com/topic/detail/12447332 https://avg.163.com/topic/detail/12447331 https://avg.163.com/topic/detail/12447330 https://avg.163.com/topic/detail/12447329 https://avg.163.com/topic/detail/12447328 https://avg.163.com/topic/detail/12447327 https://avg.163.com/topic/detail/12447326 https://avg.163.com/topic/detail/12447325 https://avg.163.com/topic/detail/12447324 https://avg.163.com/topic/detail/12447323 https://avg.163.com/topic/detail/12447322 https://avg.163.com/topic/detail/12447321 https://avg.163.com/topic/detail/12447320 https://avg.163.com/topic/detail/12447319 https://avg.163.com/topic/detail/12447318 https://avg.163.com/topic/detail/12447317 https://avg.163.com/topic/detail/12447316 https://avg.163.com/topic/detail/12447315 https://avg.163.com/topic/detail/12447314 https://avg.163.com/topic/detail/12447312 https://avg.163.com/topic/detail/12447311 https://avg.163.com/topic/detail/12447305 https://avg.163.com/topic/detail/12447307 https://avg.163.com/topic/detail/12447306 https://avg.163.com/topic/detail/12447303 https://avg.163.com/topic/detail/12447301 https://avg.163.com/topic/detail/12439550 https://avg.163.com/topic/detail/12439531 https://avg.163.com/topic/detail/12439560 https://avg.163.com/topic/detail/12439544 https://avg.163.com/topic/detail/12439547 https://avg.163.com/topic/detail/12439551 https://avg.163.com/topic/detail/12447299 https://avg.163.com/topic/detail/12447298 https://avg.163.com/topic/detail/12447297 https://avg.163.com/topic/detail/12447296 https://avg.163.com/topic/detail/12447295 https://avg.163.com/topic/detail/12447294 https://avg.163.com/topic/detail/12447293 https://avg.163.com/topic/detail/12447292 https://avg.163.com/topic/detail/12447291 https://avg.163.com/topic/detail/12447290 https://avg.163.com/topic/detail/12447288 https://avg.163.com/topic/detail/12447289 https://avg.163.com/topic/detail/12447286 https://avg.163.com/topic/detail/12447285 https://avg.163.com/topic/detail/12447284 https://avg.163.com/topic/detail/12447283 https://avg.163.com/topic/detail/12447281 https://avg.163.com/topic/detail/12447282 https://avg.163.com/topic/detail/12447280 https://avg.163.com/topic/detail/12447277 https://avg.163.com/topic/detail/12447275 https://avg.163.com/topic/detail/12439555 https://avg.163.com/topic/detail/12439517 https://avg.163.com/topic/detail/12447267 https://avg.163.com/topic/detail/12439540 https://avg.163.com/topic/detail/12447274 https://avg.163.com/topic/detail/12447273 https://avg.163.com/topic/detail/12447272 https://avg.163.com/topic/detail/12447269 https://avg.163.com/topic/detail/12447270 https://avg.163.com/topic/detail/12447271 https://avg.163.com/topic/detail/12447266 https://avg.163.com/topic/detail/12447268 https://avg.163.com/topic/detail/12447265 https://avg.163.com/topic/detail/12447264 https://avg.163.com/topic/detail/12447253 https://avg.163.com/topic/detail/12439467 https://avg.163.com/topic/detail/12439502 https://avg.163.com/topic/detail/12439498 https://avg.163.com/topic/detail/12439504 https://avg.163.com/topic/detail/12439483 https://avg.163.com/topic/detail/12439464 https://avg.163.com/topic/detail/12439472 https://avg.163.com/topic/detail/12439485 https://avg.163.com/topic/detail/12439463 https://avg.163.com/topic/detail/12447251 https://avg.163.com/topic/detail/12439473 https://avg.163.com/topic/detail/12439474 https://avg.163.com/topic/detail/12447250 https://avg.163.com/topic/detail/12447249 https://avg.163.com/topic/detail/12447248 https://avg.163.com/topic/detail/12447247 https://avg.163.com/topic/detail/12447246 https://avg.163.com/topic/detail/12447245 https://avg.163.com/topic/detail/12447244 https://avg.163.com/topic/detail/12447243 https://avg.163.com/topic/detail/12447242 https://avg.163.com/topic/detail/12447241 https://avg.163.com/topic/detail/12447240 https://avg.163.com/topic/detail/12447237 https://avg.163.com/topic/detail/12447234 https://avg.163.com/topic/detail/12447232 https://avg.163.com/topic/detail/12447236 https://avg.163.com/topic/detail/12439491 https://avg.163.com/topic/detail/12439508 https://avg.163.com/topic/detail/12439477 https://avg.163.com/topic/detail/12447228 https://avg.163.com/topic/detail/12447230 https://avg.163.com/topic/detail/12447226 https://avg.163.com/topic/detail/12447225 https://avg.163.com/topic/detail/12447222 https://avg.163.com/topic/detail/12447224 https://avg.163.com/topic/detail/12447229 https://avg.163.com/topic/detail/12447221 https://avg.163.com/topic/detail/12447220 https://avg.163.com/topic/detail/12447227 https://avg.163.com/topic/detail/12447223 https://avg.163.com/topic/detail/12447217 https://avg.163.com/topic/detail/12447215 https://avg.163.com/topic/detail/12447219 https://avg.163.com/topic/detail/12447218 https://avg.163.com/topic/detail/12447216 https://avg.163.com/topic/detail/12447213 https://avg.163.com/topic/detail/12447214 尝试一下 »

字符串（String）字面量 可以使用单引号或双引号:

"John Doe"

'John Doe'

尝试一下 »

表达式字面量 用于计算：

5 + 6 5 * 10

尝试一下 »

数组（Array）字面量 定义一个数组：

[40, 100, 1, 5, 25, 10]

对象（Object）字面量 定义一个对象：

{firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"}

函数（Function）字面量 定义一个函数：

function myFunction(a, b) { return a * b;}

JavaScript 变量

在编程语言中，变量用于存储数据值。

JavaScript 使用关键字 var 来定义变量， 使用等号来为变量赋值：

var x, length x = 5 length = 6

尝试一下 »

变量可以通过变量名访问。在指令式语言中，变量通常是可变的。字面量是一个恒定的值。

JavaScript 操作符

JavaScript使用 算术运算符 来计算值:

(5 + 6) * 10

尝试一下 »

JavaScript使用赋值运算符给变量赋值：

x = 5 y = 6 z = (x + y) * 10

尝试一下 »

JavaScript语言有多种类型的运算符：

JavaScript 语句

在 HTML 中，JavaScript 语句用于向浏览器发出命令。

语句是用分号分隔：

x = 5 + 6; y = x * 10;

JavaScript 关键字

JavaScript 关键字用于标识要执行的操作。

和其他任何编程语言一样，JavaScript 保留了一些关键字为自己所用。

var 关键字告诉浏览器创建一个新的变量：

var x = 5 + 6; var y = x * 10;

JavaScript 同样保留了一些关键字，这些关键字在当前的语言版本中并没有使用，但在以后 JavaScript 扩展中会用到。

以下是 JavaScript 中最​​重要的保留关键字（按字母顺序）：