JavaScript lesson 10: else if, &&, || and !
US version. US grades and US spelling. · UK version of this lesson
An if … else if … else chain checks the conditions in order and runs the FIRST block whose condition is true. Then the rest are skipped. A complete 40-minute JavaScript lesson for beginners (Grades 7–8), from Unit 4: Decisions. It runs right here in your browser – nothing to install.
- Time
- 40 minutes + 20 min homework
- Grade
- Grades 7–8 (ages 12–13)
- You need
- A computer or tablet, paper and a pencil
- Graded
- Instantly, with explanations
For parents: how to use this lesson
You don't need to know JavaScript yourself. The lesson explains each step on screen, the way Mr Babbage, our Head of Computing, likes it: a worked example first, then a go for your child. Code questions run your child's program in the browser – graded straight away.
- Read what your child will learn together.
- Press Start the lesson below. Sit with your child for the teaching and the worked example (about 16 minutes): ask them to say what each line does.
- Let them do the practice on their own. When code goes wrong, the error message is a clue – let them read it out and try again before you help.
- Finish with the talk question: Describe a rule from a game you know using && or ||.
Watch out for
- Every true branch in an else if chain runs. Only the first true one runs.
&&and||mean the same. Test both with one true and one false side.
Miss Lovelace's tip for home: ask your child to explain one line of their program to you in their own words. If they can explain it, they understand it – and every error message is a clue, not a failure.
What your child will learn
Learning goal: choose between several options with else if.
Success looks like
- I can choose between several options with
else if. - I can combine conditions with
&&and||. - I can flip a condition with
!.
Key words
else if · and · or · not · logical operator
What to have ready
- A device with a web browser (the code runs in the browser – nothing to install)
- Paper for tracing
- A keyboard helps for typing code (a tablet or phone works too)
The big ideas (for the adult)
An if … else if … else chain checks the conditions in order and runs the FIRST block whose condition is true. Then the rest are skipped.
&& (and) is true only when both sides are true. || (or) is true when at least one side is true. ! (not) flips true and false.
Put the most specific check first: in FizzBuzz, check "divides by 3 and 5" before "divides by 3".
Worked example – see it
const day = "Fri"
if (day === "Sat" || day === "Sun") {
console.log("weekend")
} else {
console.log("school day")
}It prints:
school day
The lesson, step by step
| Part | Time | How it is checked |
|---|---|---|
| Starter | 5 min | Graded by Classfern |
| Teaching input | 8 min | Read, watch and talk |
| See it, then predict | 8 min | Graded by Classfern |
| Put it in order, write it, fix it | 14 min | Graded by Classfern |
| Closure and exit ticket | 5 min | Graded by Classfern + self-check |
The lesson
It runs here on the page. No sign-up and no names – progress is kept only in this browser. Each visit picks a new mix of questions.
Homework
20 minutes: 7 questions – predict what code prints, write or fix a short program, and check the key ideas – then a short reflection. New questions every time, all graded instantly.
Practice tests
Curriculum
CSTA K–12 Computer Science Standards (2017), grades 6–8: 2-AP-12 – Design and iteratively develop programs with control structures incl. nested loops and compound conditionals.
The standard codes are CSTA's; the descriptions are our own words.
Our lessons and questions are our own. They are not written or endorsed by any government department, testing agency or exam board. JavaScript is a trademark or registered trademark of Oracle Corporation in the U.S. and other countries; Classfern is not affiliated with or endorsed by it.