Combining conditions in JavaScript

Although the operation && takes precedence over ||, it is often more convenient to use grouping parentheses to explicitly indicate the precedence of operations:

let num = 3;

if ( (num > 0 && num < 5) || (num > 10 && num < 20) ) {
	console.log('+++');
} else {
	console.log('---');
}

Of course, grouping can also be used when you need your own priority of operations, and not the one that is obtained by default:

let num1 = 3;
let num2 = 5;

if ( num1 > 0 && (num2 == 3 || num2 == 5) ) {
	console.log('+++');
} else {
	console.log('---');
}

In the code below, specify the precedence of operations explicitly:

let num = 3;
		
if (num > 5 && num < 10 || num == 20) {
	console.log('+++');
} else {
	console.log('---');
}

In the code below, specify the precedence of operations explicitly:

let num = 3;
		
if (num > 5 || num > 0 && num < 3) {
	console.log('+++');
} else {
	console.log('---');
}

In the code below, specify the precedence of operations explicitly:

let num = 3;
		
if (num == 9 || num > 10 && num < 20 || num > 20 && num < 30) {
	console.log('+++');
} else {
	console.log('---');
}