JavaScript iteration
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JavaScript iteration

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This is the slides for the YouTube video i did on this subject

This is the slides for the YouTube video i did on this subject

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JavaScript iteration Presentation Transcript

  • 1. JavaScript Iterations Charles Russell Bennu Bird Media
  • 2. Changes in Direction ● In the previous video we allowed our program to change flow to one of many different program blocks ● But that is not the only direction change we may want. It is often desireable to repeatedly execute the same block ● Looking for some value in a list ● Sending a group email ● In other words we want to loop
  • 3. The While loop ● At the top of the loop the condition is checked ● If the condition is met then execute code block ● Loop will continue until condition not met. while (conditional expression) { //Do some stuff } ● Be sure that eventually the condition will not be met otherwise you get an infinite loop;
  • 4. The Do loop ● At the bottom of the loop condition is checked ● Assures the code block will be executed at least once ● Loop continues until condition false do { //code to execute goes here } while (conditional expression);
  • 5. Basic For loop ● Executes the loop a number of times ● Has three statements ● First excutes before the loop is executed – Usually used for initialization ● Second conditional expression – Code executes if true ● Third – Executes after the code block before the next iteration
  • 6. Basic For Syntax for (init ; conditional exp; prepForNext) { //do some stuff }
  • 7. For looping through properties ● Used to examine properties of an object ● Important to filter as all properties examined even those inherited from parent and its parent.... for (variable in Object) { if ( Object.hasOwnProperty(variable) { //code to execute } }
  • 8. Cutting the loop ● break ● Halts code execution in the loop – Stop further execution of code block and exit the loop ● continue ● Halts execution of the rest of the code block ● Continues next iteration
  • 9. Summary ● Iteration is another word for looping ● While loops check for conditional at the top of the loop ● Be wary of the infinite loop ● Do loops check conditional at bottom of the loop ● Basic for loops allow loops to be controlled by number of executions ● For in loops will check properties of Objects and Arrays ● Be sure to use hasOwnProperty method.
  • 10. Next: Live Code