A debugging problem caused by the JS semicolon _ javascript skills

Let's take a look at the effect after the execution. Whatever the value of textbox1.text is, the conditional judgment will be applied. Why? Let's look at the code below:
Var a = textbox1.text;
Var B = 5;
If ( {
A = B;
}
Let's see what effect the execution has. No matter what value textbox1.text is, it will be judged by conditions. Why? Are there any discoveries.
When I was writing code, if ( Note: As I wrote it, when I opened it again, there was no content, so I simplified it a bit. I wrote a rough description.