The difference between ++a and a++ in js

In JavaScript, a and a are both unary increment operators. The former increments first and then outputs, and the latter outputs first and then increments. The former has a higher priority and is executed before arithmetic operators.

##In JavaScript, a and a

In JavaScript,

a and a are all unary operators, used to increment the value of a variable. However, there is a key difference between them:

a (prefix increment)

First increments the value of the variable by 1, and then returns the incremented value.
• The value of expression a is the incremented value.

a (suffix increment)

Returns the current value of the variable first, and then increments the variable's value by 1.
• The value of expression a is the value before incrementing.

Example:

<code class="js">let a = 5;

console.log(++a); // 返回 6，将 a 的值递增 1 后输出
console.log(a); // 输出 6

console.log(a++); // 返回 6，输出 a 的当前值
console.log(a); // 输出 7，将 a 的值在输出后递增 1</code>

Another difference:

In JavaScript,

a Operators have higher precedence (than arithmetic operators). This means that when an expression contains both a and an arithmetic operator, a will be executed first.

Example:

<code class="js">let a = 5;

console.log(a + ++a); // 返回 12，先递增 a，然后再执行加法
console.log(a + a++); // 返回 11，先执行加法，再递增 a</code>

In short,

a increments first and then outputs, a outputs first and then increments. Understanding the difference between these two operators is critical to writing clear, unambiguous JavaScript code.

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