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Precedence & Associativity

Precedence determines the order in which operators are evaluated in an expression.
For example, 3 + 4 * 5 returns 23, because * is evaluated before +.
* is said to have higher precedence than +.

Associativity determines the order of evaluation for operators of the same precedence.
For example, a = b = c will assign both variables a and b the value of c, because b = c will be evaluated first, as = has right-to-left associativity.

console.log(3 * (5 + 2));
console.log(2 ** 2 ** 2 * 3 % 10);

console.log(3 * (5 + 2));
console.log(2 ** 2 ** 2 * 3 % 10);

Note that an assignment statement returns the value being assigned. Because of the right-to-left associativity of some operators, you can declare multiple variables/functions using the operators continuously in a row:

var x = y = 7;
console.log(z = x += 1);
f = a => b => x;
console.log(f()()); // f() and 'a' return a function

var x = y = 7;
console.log(z = x += 1);
f = a => b => x;
console.log(f()()); // f() and 'a' return a function