操作符

基本的操作符允许你操作数值。

// Concatenation
var foo = "hello";
var bar = "world";
console.log( foo + " " + bar ); // "hello world"

/ Multiplication and division
2 * 3;
2 / 3;

// Incrementing and decrementing
// The pre-increment operator increments the operand before any further processing.
var i = 1;
console.log( ++i ); // 2 - because i was incremented before evaluation
console.log( i ); // 2
// The post-increment operator increments the operand after processing it.
var i = 1;
console.log( i++ ); // 1 - because i was evaluated to 1 and _then_ incremented
console.log( i ); // 2 - incremented after using it

作用于数字和字符串的操作符

在javascript中，字符和数字偶尔会有意想不到的行为

// Addition vs. Concatenation
var foo = 1;
var bar = "2";
console.log( foo + bar ); // 12

// Coercing a string to act as a number:
var foo = 1;
var bar = "2";
console.log( foo + Number(bar) ); // 3

当数字构造被当作函数调用时（如上例），它就会有把它的参数转换为数字的效果。单元加（+）操作符也可以做同样的事情。

// Forcing a string to act as a number (using the unary plus operator):
console.log( foo + +bar ); // 3