feat: Add article about JavaScript conditions

Author: lfavole

content/blog/javascript-conditions.md

@@ -0,0 +1,103 @@
++++
+title = "This JavaScript condition is very strange..."
+date = 2025-03-28
++++
+
+# This JavaScript condition is very strange...
+
+I was writing [this code](https://github.com/lfavole/lfavole.github.io/blob/1a7b1f5/content/blog/trigonometrie/trigonometrie.js#L153)...
+<div style="cursor: not-allowed; user-select: none">
+
+```javascript
+class Fraction {
+    // snip
+
+    toString() {
+        if (this.numerator === 0)
+            return "0";
+        let result = "";
+        if (this.constructor.SYMBOL)
+            if (this.numerator === -1)
+                result += "-";
+        else
+            result += this.numerator;
+        result += this.constructor.SYMBOL;
+        if (this.denominator !== 1)
+            result += "/" + this.denominator;
+        return result;
+    }
+}
+
+class PiFraction extends Fraction {
+    static SYMBOL = "π";
+}
+```
+
+</div>
+
+but I quickly saw that it was doing the wrong thing, e.g.
+> `» new PiFraction(1, 4).toString()`<br>
+> `← "1π/4"`
+
+which is not a fully simplified fraction.
+
+I ended up finding the error, which was:
+```javascript
+class Fraction {
+    toString() {
+        // snip
+        if (this.constructor.SYMBOL) {
+            if (this.numerator === -1) {
+                result += "-";
+            }
+        } else {
+            result += this.numerator;
+        }
+        // snip
+    }
+}
+```
+which was what I meant when indenting the code, but the JavaScript compiler didn't understand it
+and compiled the nested conditional first.
+
+So if you write this:
+<div style="cursor: not-allowed; user-select: none">
+
+```javascript
+if (a)
+    if (b)
+        c();
+else
+    d();
+```
+
+</div>
+
+Be careful, because it gets evaluated as:
+<div style="cursor: not-allowed; user-select: none">
+
+```javascript
+if (a) {
+    if (b) {
+        c();
+    }
+else {
+    d();
+}}
+```
+
+</div>
+
+and NOT as:
+```javascript
+if (a) {
+    if (b) {
+        c();
+    }
+} else {
+    d();
+}
+```
+as you would expect it.
+
+The last code snippet is the only one that you should use.