Add JS prefix/postfix

blog_posts/javascript-prefix-postfix-operators.md

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+---
+title: What is the difference between prefix and postfix operators?
+type: question
+tags: javascript,math
+authors: chalarangelo
+cover: blog_images/plant-candle.jpg
+excerpt: While both the prefix and postfix operators increment a value, the resulting value of the expression is very different.
+firstSeen: 2021-10-31T05:00:00-04:00
+---
+
+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--`).
+
+If used prefix, the value is incremented/decremented, and the value of the expression is the updated value.
+
+```js
+let i = 0;    // i = 0
+let j = ++i;  // i = 1, j = 1
+let k = --i;  // i = 0, k = 0
+```
+
+If used postfix, the value is incremented/decremented, and the value of the expression is the original value.
+
+```js
+let i = 0;    // i = 0
+let j = i++;  // i = 1, j = 0
+let k = i--;  // i = 0, k = 1
+```