Logical operators play a vital role in JavaScript, a robust and versatile programming language commonly utilized in web development. Among the fundamental logical operators in JavaScript designed for executing logical operations is the logical AND (&&) operator.
When all Boolean values within an array are true, the logical AND (&&) operator will evaluate to true. However, if any of the operands fails to meet the condition, the result will be false.
In a broader sense, the operator provides the final operand's value if all operands are true. The first false or incorrect operand's value is identified as the condition is evaluated sequentially from left to right.
This article will extensively discuss the syntax, uses, and practical illustrations of the AND operator.
What is the JS AND (&&) operator?
When both operands are true, the logical AND (&&) operator evaluates to true; it returns false if at least one operand is false.
Syntax
The syntax demonstrates the condition along with the "AND" operator.
expression1 && expression2
Description:
When the logical AND (&&) operator evaluates operands sequentially from left to right, it returns the value of the first false operand encountered immediately. If all operands are true, the operator returns the value of the last operand in the sequence.
A value is deemed true when it can be converted to a true state, and it is regarded as false when it can be altered to a false state.
Expressions that can be changed to false include the following examples:
- false;
- null;
- NaN;
- empty string ("" or '' or ``);
- undefined.
JavaScript AND operator condition
The Boolean value is visible as output when the condition is satisfied by the operator. Below is a table illustrating the potential results of the && operator:
| Expression 1 / first operand | Expression 2 / second operands | Result |
|---|---|---|
true |
true | true |
true |
false | false |
| false | true | false |
| false | false | false |
Example: Basic AND operator
In the presented illustration, we demonstrate the fundamental AND operator along with its Boolean representation.
Example
<!DOCTYPE html>
<html>
<body style="background-color:beige;">
<h2> JavaScript Basic AND Operator </h2>
<script>
document.writeln(true && true); // Output: true
document.writeln("<br>");
document.writeln(true && false); // Output: false
document.writeln("<br>");
document.writeln(false && true); // Output: false
document.writeln("<br>");
document.writeln(false && false); // Output: false
</script>
</body>
</html>
Output:
The output shows the result of the && operator.
Example: Basic AND operator with variable
The provided illustration demonstrates the fundamental usage of the AND operator in conjunction with variables to evaluate conditions. When the values of two variables are identical, the output will display the first specified result.
Example
<!DOCTYPE html>
<html>
<body style="background-color:beige;">
<h2> JavaScript Basic AND Operator with variable </h2>
<script>
let X = true;
let Y = true;
if (X && Y) {
document.writeln("You are allowed to Study JavaScript.");
} else {
document.writeln("Entry denied to Study JavaScript");
}
</script>
</body>
</html>
Output:
The result displayed is the outcome of employing the && operator with the variable.
Example: Basic AND operator with a Boolean value
Below is an illustration demonstrating the fundamental use of the AND operator with a Boolean value.
Example
<!DOCTYPE html>
<html>
<body style="background-color:beige;">
<h3> JavaScript AND Operator with the Boolean value </h3>
<script>
const a = 3;
const b = -2;
document.writeln(a > 0 && b > 0);
document.writeln("<br>");
document.writeln(a > 0 && b < 0);
document.writeln("<br>");
document.writeln(a > 0 && b < 0);
document.writeln("<br>");
</script>
</body>
</html>
Output:
The result displayed is the outcome of applying the && operator to a Boolean value.
JS AND operator preserves Non-Boolean
While the && operator can operate on operands that are not strictly boolean, the outcome can always be converted into a Boolean primitive, effectively functioning as a Boolean operator. To explicitly convert the result into a Boolean value, you can utilize the Boolean constructor or employ the double NOT operator on the return value of the expression.
Example:
The illustration below demonstrates the fundamental usage of the AND operator and its output in a Non-Boolean format.
Example
<!DOCTYPE html>
<html>
<body style="background-color:beige;">
<h3> JavaScript AND Operator with Non-Boolean value </h3>
<script>
var result1 = "" && "foo"; // result is assigned "" (empty string)
document.writeln("output: "+result1);
var result2 = 2 && 0; // result is assigned 0
document.writeln("<br> output: "+result2);
var result3 = "foo" && 4; // result is assigned 4
document.writeln("<br> output: "+result3);
</script>
</body>
</html>
Output:
The result displayed is the outcome of applying the && operator to a value that is not a Boolean.
Short-circuit evaluation
The short-circuit operator functions as the logical AND operator. When each operand is converted into a Boolean value, the AND operator stops evaluating any remaining operands. Instead, it immediately returns the initial value of the operand that was found to be false after the conversion.
Syntax:
Below is an example of the syntax used for implementing short circuit evaluation.
(some false expression) && expr
Description:
When the initial operand (an untrue statement) is assessed as false, the expr section does not undergo evaluation. If expr represents a function, the function is not called.
Example:
The forthcoming instance demonstrates the fundamental usage of the AND operator along with its short-circuit evaluation criterion.
Example
<!DOCTYPE html>
<html>
<body style="background-color:beige;">
<h3> JavaScript AND Operator with short circuit function </h3>
<script>
function A() {
console.log("called A");
return false;
}
function B() {
console.log("called B");
return true;
}
document.writeln("Both function shows same values: ");
document.writeln(A() && B());
</script>
</body>
</html>
Output:
The result displayed is the outcome of using the && operator with short-circuit evaluation.
Operator precedence
The logical AND operator, represented by &&, is prioritized over the logical OR operator, which is denoted by ||, due to the higher precedence of the AND operator in programming languages.
Example
The illustration below demonstrates the fundamental usage of the AND operator and its precedence in operators.
Example
<!DOCTYPE html>
<html>
<body style="background-color:beige;">
<h3> JavaScript AND Operator with Operator precedence </h3>
<script>
var a1 = true || false && false; // true
document.writeln(a1);
document.writeln("<br>");
var a2 = true && (false || false); // false
document.writeln(a2);
document.writeln("<br>");
var a3 = (2 === 3) || (4 < 0) && (1 === 1); // false
document.writeln(a3);
document.writeln("<br>");
</script>
</body>
</html>
Output:
The result displayed is the outcome of using the && operator considering its precedence in operations.
Removing nested parentheses
When specific conditions are met, it is always possible to eliminate the parentheses from a complicated expression because logical expressions are assessed in a left-to-right manner.
Example:
The subsequent demonstration illustrates the fundamental usage of the AND operator without nested parentheses.
Example
<!DOCTYPE html>
<html>
<body style="background-color:beige;">
<h3> JavaScript AND Operator with nested parentheses removed</h3>
<script>
var a1 = true || false && false; // true
document.writeln(a1);
document.writeln("<br>");
var a2 = true && (false || false); // false
document.writeln(a2);
document.writeln("<br>");
var a3 = (2 === 3) || (4 < 0) && (1 === 1); // false
document.writeln(a3);
document.writeln("<br>");
</script>
</body>
</html>
Output:
The result displayed is the outcome of using the && operator without the nested parentheses.
JavaScript AND Operator with Ternary Operator
Within JavaScript, there exists a conditional operator that allows for the assignment of a value depending on a specified variable and its condition.
Syntax:
The syntax below demonstrates the concurrent use of the ternary and logical AND operators.
variablename = (condition) ? value1:value2
Example:
Below is an illustration demonstrating the ternary operator in conjunction with the AND logical operator:
Example
<!DOCTYPE html>
<html>
<body style="background-color:beige;">
<h1>JavaScript Ternary Operator with AND logical Operator</h1>
<h2>The && with Ternary Operator</h2>
<p>Input your age and click the button:</p>
<input id="age" value="18" />
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
let age = document.getElementById("age").value;
let voteable = ((age >= 18) && (age <= 50)) ? "Applicable":"Not Applicable";
document.getElementById("demo").innerHTML = voteable + " to vote.";
}
</script>
</body>
</html>
Output:
The result of using the && operator in conjunction with the ternary operator is displayed in the output.
The AND (&&) Operator Features
- Logical Evaluation: Only when both operands are true then only it returns true.
- Short-circuiting: The second operand is not evaluated if the first operand is false.
- It gives back values instead of just Booleans: Either the final true operand or the first false operand.
- Used in Conditional Statements: Often used to combine several conditions in if
- Works with a Variety of Data Types: Arrays, objects, strings, numbers, and more can all be used.
- Short-Circuiting Enhances Efficiency: JavaScript improves efficiency by not evaluating the second condition if the first condition is false.
- Conditional statements are made simpler: Enables the use of concise conditions rather than several if statements.
- Beneficial for Assignments of Default Values: When a condition is satisfied, it can be utilized in expressions to assign values.
- Encourages Non-Boolean Principles: It can return actual values rather than only true or false, in contrast to strict logical conditions.
- Unusual Conduct with Non-Boolean Values If not treated correctly, it can produce surprising results because it returns either the last true value or the first false value.
- Debugging Complex Expressions is Hard It can complicate debugging when paired with several data formats and multiple circumstances.
- Not Always Easy for Beginners to Understand When it returns a value that is not Boolean, developers who only anticipate true or false outputs may become perplexed.
- Not Acceptable as a Default Assignment for Nullish Values (null or undefined) The nullish coalescing operator (??) functions as a backup for null or undefined data, but the && operator does not.
The AND (&&) Operator Benefits
The AND (&&) Operator drawbacks
Conclusion
An essential element in JavaScript, the logical AND (&&) operator is commonly used for conditional execution, short-circuit evaluations, and logical expressions. Understanding its functionality can help students create more efficient and accurate JavaScript code.