Understanding JavaScript Operator Precedence

In JavaScript, operator precedence determines the order in which operators are evaluated in an expression. Understanding operator precedence is crucial for writing correct and efficient code. This tutorial will cover the basics of JavaScript operator precedence, providing detailed explanations and sample codes for different scenarios.

JavaScript Operator Precedence

JavaScript follows a set of rules to determine the order in which operators are evaluated in an expression. Operators with higher precedence are evaluated first. If two operators have the same precedence, their evaluation order depends on their associativity.

Operator Precedence Table

JavaScript has various types of operators, each with its own precedence level. Below is a simplified table showing some common operators and their precedence levels:

Precedence	Operator
1 (highest)	() (grouping)
2	! (logical NOT), ++ (postfix), — (postfix)
3	*, /, %
4	+, –
5	<, >, <=, >=
6	==, !=, ===, !==
7	&& (logical AND)
8	|| (logical OR)
9 (lowest)	= (assignment)

Sample Codes

Let’s go through some sample code snippets to understand how operator precedence works in JavaScript.

Scenario 1: Arithmetic Operations

let result = 5 + 3 * 2;
console.log(result); // Output: 11

Explanation:

• Multiplication (*) has higher precedence than addition (+).
• So, 3 * 2 is evaluated first, resulting in 6.
• Then, 5 + 6 is evaluated, resulting in 11.

Scenario 2: Comparison Operators

let result = 10 > 5 + 3;
console.log(result); // Output: true

Explanation:

• Addition (+) has lower precedence than comparison (>).
• So, 5 + 3 is evaluated first, resulting in 8.
• Then, 10 > 8 is evaluated, resulting in true.

Scenario 3: Logical Operators

let result = (5 > 3) && (10 < 5);
console.log(result); // Output: false

Explanation:

• Comparison operators have higher precedence than logical operators.
• So, (5 > 3) and (10 < 5) are evaluated first.
• 5 > 3 is true, but 10 < 5 is false.
• Then, true && false evaluates to false.

Conclusion

Understanding operator precedence is essential for writing JavaScript code that behaves as expected. By following the rules of operator precedence, you can avoid unexpected outcomes and write more efficient code. Make sure to refer to the operator precedence table whenever you’re unsure about the order of evaluation in complex expressions. Practice writing and analyzing code to solidify your understanding of JavaScript operator precedence.