blocks|key|216267|text|a+=+1
b+=+-a
console.log(b)

output
-1|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|216268|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>a = 1
b = -a
console.log(b)

output
-1
</code></pre>

blocks|key|216594|text|%2B操作符不改变值的符号，而-操作符改变符号。这两个运算符的结果都取决于原始值的符号，无论原始符号如何，都不会使值为正或负值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|216595|var+a+=+4;
a+=+-a;+//+-4
a+=+%2Ba;+//+-4|code-block|syntax|javascript|216596|abs函数执行您认为%2B运算符执行的操作；它使值为正，而不考虑原始符号。|216597|var+a+=-4;
a+=+Math.abs(a);+//+4|216598|执行%2Ba实际上与执行a+*+1相同；如果需要，它会将a中的值转换为一个数字，但之后不会更改该值。|216599|var+a+=+"5";
a+=+%2Ba;+//+5|216600|%2B运算符有时用于将字符串转换为数字，但您可以使用parseInt和parseFloat函数以更具体的方式进行转换。|216601|var+a+=+"5";
a+=+parseInt(a,+10);+//5|216602|entityMap^0|0|1|D|1|0|0|0|3|A|1|0|0|2|2|A|5|Q|1|0|0|0|1|O|8|X|A|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1H|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]|$9|1N|A|1O|B|C]]|D|@]|E|$]]|$1|U|3|V|5|H|7|1P|8|@]|D|@]|E|$I|J]]|$1|W|3|-4|5|6|7|1Q|8|@]|D|@]|E|$]]]|X|$]]

The <code>+</code> operator doesn't change the sign of the value, and the <code>-</code> operator does change the sign. The outcome of both operators depend on the sign of the original value, neither operator makes the value positive or negative regardless of the original sign.

<pre><code>var a = 4;
a = -a; // -4
a = +a; // -4
</code></pre>

The <code>abs</code> function does what you think that the <code>+</code> opreator does; it makes the value positive regardless of the original sign.

<pre><code>var a =-4;
a = Math.abs(a); // 4
</code></pre>

Doing <code>+a</code> is practically the same as doing <code>a * 1</code>; it converts the value in <code>a</code> to a number if needed, but after that it doesn't change the value.

<pre><code>var a = "5";
a = +a; // 5
</code></pre>

The <code>+</code> operator is used sometimes to convert string to numbers, but you have the <code>parseInt</code> and <code>parseFloat</code> functions for doing the conversion in a more specific way.

<pre><code>var a = "5";
a = parseInt(a, 10); //5
</code></pre>

blocks|key|213404|text|一个例子是，它们可以用于将字符串转换为数字，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|213405|var+threeStr+=+'3.0'
var+three+=+%2BthreeStr
console.log(threeStr+%2B+3)+//+'3.03'
console.log(three+%2B+3)+//6|code-block|syntax|javascript|213406|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

One example is that they can be used to convert a string to a number, 

<pre><code>var threeStr = '3.0'
var three = +threeStr
console.log(threeStr + 3) // '3.03'
console.log(three + 3) //6
</code></pre>

blocks|key|2862014|text|尝尝这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2862015|false+==+0+//+returns+true|code-block|syntax|javascript|2862016|所以,|2862017|a+=+false

a+=+%2Ba+//a+*+1

console.log(a)+//+prints+0+as+expected|2862018|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Try this

<pre><code>false == 0 // returns true
</code></pre>

So, 

<pre><code>a = false

a = +a //a * 1

console.log(a) // prints 0 as expected
</code></pre>

blocks|key|2862057|text|变量'a‘中的'%2B’运算符简单地表示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2862058|变量'a‘中的'-’运算符仅表示：-a|2862059|Since,+in+above+example+
a=-10;
a=+%2Ba;+//+means+a,+ie,+%2B(-10)+which+is+-10

but,
a=+-a;++//+means+-a,+ie,+-(-10)+which+is+%2B10|code-block|syntax|javascript|2862060|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

'+' operator in a variable 'a' simply means : a

'-' operator in a variable 'a' simply means : -a

<pre><code>Since, in above example 
a=-10;
a= +a; // means a, ie, +(-10) which is -10

but,
a= -a; // means -a, ie, -(-10) which is +10
</code></pre>

blocks|key|216378|text|我想从基本的数学角度来解释这一点：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|216379|乘法规则：|216380|Positive+x+Positive+=+Positive:+3+x+2+=+6++
Negative+x+Negative+=+Positive:+(-2)+x+(-8)+=+16+++
Negative+x+Positive+=+Negative:+(-3)+x+4+=+-12++
Positive+x+Negative+=+Negative:+3+x+(-4)+=+-12++|code-block|syntax|javascript|216381|考虑到你的例子：|216382|a+=+-10;
a+=+%2Ba
document.writeln(a);|216383|%2Ba+=+%2B(+-10+)+=正x负=负=-10|216384|a+=+false;
a+=+%2Ba;
document.writeln(a);|216385|false+==+0，%2Ba+=+%2B(%2B0)+=正*正=正=0(可能使用true是更好的例子)|216386|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

I would like to explain this from basic mathematical point: 
The multiplying rules: 

<pre><code>Positive x Positive = Positive: 3 x 2 = 6 
Negative x Negative = Positive: (-2) x (-8) = 16 
Negative x Positive = Negative: (-3) x 4 = -12 
Positive x Negative = Negative: 3 x (-4) = -12 
</code></pre>

Considering you example:

<pre><code>a = -10;
a = +a
document.writeln(a);
</code></pre>

+a = +(-10) = Positive x Negative = Negative = -10

<pre><code>a = false;
a = +a;
document.writeln(a);
</code></pre>

false == 0, +a = +(+0) = Positive * Positive = Positive = 0 (maybe use true is a better example)

blocks|key|213486|text|%2Ba表示a*1，-a表示a*(-1)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|213487|就是这样！|213488|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

+a means a*1
and 
-a means a*(-1)

Thats it!!!!!!

I'm trying to understand unary operators in javascript, I found this guide here <a href="http://wiki.answers.com/Q/What_are_unary_operators_in_javascript" rel="noreferrer">http://wiki.answers.com/Q/What_are_unary_operators_in_javascript</a> most of it makes sense but what I don't understand is how the following examples would be used in an actual code example:

<pre><code>+a;
-a;
</code></pre>

To my understanding the +a; is meant to make the variable the positive value of a and the -a; is meant to make the variable the negative value of a. I've tried a number of examples like:

<pre><code>a = -10;
a = +a;
document.writeln(a);
</code></pre>

And the output is still -10;

I've also tried:

<pre><code>a = false;
a = +a;
document.writeln(a);
</code></pre>

And the output is 0;

What is a practical code example of these unary operators?

Explain +var and -var unary operator in javascript

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

我正在尝试理解javascript中的一元运算符，我发现这里的指南大部分都很有意义，但我不理解的是如何在实际的代码示例中使用以下示例：+a;-a;根据我的理解，+ a ;的意思是使变量为a的正值，-a的意思是使变量为a的负值。我尝试了许多示例，例如：a = -10;a = +a;document.writeln(a);...

问javascript中的Explain +var和-var一元运算符
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问javascript中的Explain +var和-var一元运算符EN