1. Introduction to For Loops
See Beginning JavaScript
(Paul Wilton) p. 87
CSD 340 (Blum)

2. For Loop Example
CSD 340 (Blum)

3. Result in browser
CSD 340 (Blum)

4. SomeHTML+="All work and no play makes Jack a dull boy. "; }
var SomeHTML="";
for(i=1; i<=100;i++) {
SomeHTML+="All work and no play makes Jack a dull boy. "; }
document.write(SomeHTML);
for keyword that indicates a for loop repetitive structure
i=1 where we start counting the iterations
i<=100 condition under which we will continue to count
i++ the incrementing — this does the counting, the changing of the counting variable, in this case by 1. It could also be written i=i+1 or i+=1
The parts above are in parentheses and separated by semicolons. Then comes a set a curly brackets. The line(s) of code in the curly brackets constitute a single “iteration.”
CSD 340 (Blum)

5. Variation
There are 3 loops this time; the middle one changes the iteration code (inside the curly brackets) somewhat.
CSD 340 (Blum)

6. Variation Result
CSD 340 (Blum)

7. Second Variation
The counting variable is concatenated with the text – so that the counting is seen on the page.
CSD 340 (Blum)

8. Second Variation Result
CSD 340 (Blum)

9. Third Variation That’s two minus signs in a row.
A change in the initialization (starting point) to start at 10, a change in the condition appropriate to counting down, a change from incrementing to decrementing.
CSD 340 (Blum)

10. Third Variation Result
CSD 340 (Blum)