加法赋值 (+=)

¥Syntax

x += y

¥Description

x += y 与 x = x + y 等效，只是表达式 x 仅计算一次。

¥x += y is equivalent to x = x + y, except that the expression x is only evaluated once.

¥Examples

¥Addition assignment using numbers

let bar = 5;
bar += 2; // 7

其他非字符串、非 BigInt 值被强制转换为数字：

¥Other non-string, non-BigInt values are coerced to numbers:

let baz = true;
baz += 1; // 2
baz += false; // 2

¥Addition assignment using BigInts

let x = 1n;
x += 2n; // 3n

x += 1; // TypeError: Cannot mix BigInt and other types, use explicit conversions

¥Addition assignment using strings

let foo = "foo";
foo += false; // "foofalse"
foo += "bar"; // "foofalsebar"

let bar = 5;
bar += "foo"; // "5foo"

¥See also

• JS 指南中的赋值运算符
• 添加 (+)