Introduction to Programming in JavaScript & Data Abstraction

1. Introduction to Programming(in JavaScript) David Stotts Computer Science Department UNC Chapel Hill

2. The Big Six(6) Data Abstraction 0. data (types, simple information) 1. data storage (variables, assignment) 2. data retrieval (expressions, evaluation) 3. repetition (loops) 4. decision making (conditionals) 5. procedure abstraction (functions) 6. data abstraction (arrays) 7. objects: all-the-above, wrapped up

3. We have been studying Arrays

4. We have seen “for loops” as access patterns

5. Loop Body Contains any valid statements… • assignment • conditionals for (i=0; i<length; i++) { sum = sum + grade[ i ] ; if (grade[i]>90) { aCount = aCount + 1; } }

6. What if loop body contains… Another complete loop?

7. Loops in Loops • We call them “nested ” loops

8. Nested For Loops for (i=0; i<length; i++) { . . . for (k=i; k<length; k++) { . . . } . . . } inner loop, enclosed in outer outer loop, enclosing

9. Anyone from DC? This is the fabulous Capital Beltway...

10. Capital Beltway • A.K.A...

11. The “Inner Loop”

12. and the “Outer Loop”

13. Inner and Outer Loops

14. Nested For Loops for (i=0; i<length; i++) { . . . for (k=i; k<length; k++) { . . . } . . . } inner loop outer loop

15. Nested For Loops for (i=0; i<length; i++) { . . . for (k=i; k<length; k++) { . . . } . . . } many inner iterations inner loop outer loop 1 outer iteration

16. A Note on Indentation Formatting is CRITICAL for comprehension for (i=0; i<length; i++) { sum = sum + grade[ i ] ; if (grade[i]>90) { aCount= aCount + 1; } else { bfCount= bfCount + 1; } total += 1; }

17. A Note on Indentation Indent, block structure, be consistent for (i=0; i<length; i++) { sum = sum + grade[ i ] ; if (grade[i]>90) { aCount= aCount + 1; } else { bfCount++; } total += 1; }