29 lines
1.0 KiB
Markdown
29 lines
1.0 KiB
Markdown
---
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title: What is the difference between prefix and postfix operators?
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shortTitle: Prefix and postfix operators
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type: question
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tags: javascript,math
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author: chalarangelo
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cover: blog_images/plant-candle.jpg
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excerpt: While both the prefix and postfix operators increment a value, the resulting value of the expression is very different.
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firstSeen: 2021-10-31T05:00:00-04:00
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---
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The increment operator (`++`) adds `1` to its operand and returns a value. Similarly, the decrement operator (`--`) subtracts `1` from its operand and returns a value. Both of these operators can be used either prefix (`++i`, `--i`) or postfix (`i++`, `i--`).
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If used prefix, the value is incremented/decremented, and the value of the expression is the updated value.
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```js
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let i = 0; // i = 0
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let j = ++i; // i = 1, j = 1
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let k = --i; // i = 0, k = 0
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```
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If used postfix, the value is incremented/decremented, and the value of the expression is the original value.
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```js
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let i = 0; // i = 0
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let j = i++; // i = 1, j = 0
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let k = i--; // i = 0, k = 1
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```
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