More About Operators and Expressions

CS133JS Beginning Programming: JavaScript

Topics by Week
1. Intro to JavaScript programming	6. Arrays
2. Functions, Variable scope, Operators and Expressions	7. Functions
3. Conditional Statements	8. Objects
4. Loops	9. DOM
5. Midterm	10. Final

ReviewMath OperatorsComparison OperatorsMore on Operators and ExpressionsCombined assignment and math operatorsThe range of numbers that can be representedRepresentation of infinityReference

Review

Math Operators

JavaScript has all the math operators you know: +, -, /, * and one you might not: % (the modulo operator)


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var remainder = 8 % 3;
console.log(remainder);

There are increment and decrement operators:

postfix: x++, x--
prefix: ++x, --x


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 var count = 1;
 count++
 console.log(count);
 console.log(count++);
 console.log(count);
 console.log(++count);
 console.log(count);

Comparison Operators

More on Operators and Expressions

Review: An expression is a unit of code that can be evaluated to some value.

Combined assignment and math operators

You can shorten the way you write statements that do a math operation and assign the result to a variable. For example a = a + 5 can be shorted to a += 5. Here are more examples:


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var num = 4;
num += 2;
console.log(num);
num -= 3;
console.log(num);
num *= 10;
console.log(num);
num /= 5;
console.log(num);
num %= 2;
console.log(num);

The range of numbers that can be represented

Run this code in the console to see what the limits are for numeric expressions in JavaScript.


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 var biggestNum = Number.MAX_VALUE; 
 var smallestNum = Number.MIN_VALUE; 
 var infiniteNum = Number.POSITIVE_INFINITY; 
 var negInfiniteNum = Number.NEGATIVE_INFINITY; 
 var biggestInt = 9007199254740991; 
 var smallestInt = -9007199254740991;

Representation of infinity

Test an expression to see if it is finite: isFinite(n)
Try this with 1/0 in place of n.
Test an expression to see if it is a valid number: isNaN(n)

Reference

MDN Reference: Number

Beginning JavaScript Lecture Notes by Brian Bird, written 2018, revised 2022, are licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.


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