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- // -----Loops----- //
- /* For loops are great tools for iterating over individual elements within an array
- to work with them. A for loop has three sections within its proceeding parentheses: an
- initialization, conditional statement, and a final expression. The initialization phase
- usually declares a variable. The conditional statement phase tells the loop when to stop,
- and the final expression performs an action at the end, usually incrementing or
- decrementing a counter: */
- "use strict";
- var arr = ["What is love?", "I love you", "I hate you", 24, "Baby, don't hurt me"];
- for (var i = 0; i < arr.length; i++) {
- if (i === 0 || i === 4) {
- console.log(arr[i]);
- }
- }
- /* It is possible to loop through the array in more than one direction: */
- for (var i = arr.length; i > 0; i--) {
- if (i === 2) {
- console.log(arr[i]);
- }
- }
- /* a while loop is similar to a for loop, except a while loop only contains a conditional
- statement within its parentheses. It will require a counter of some sort to tell the loop
- when to stop. This counter is easy to forget but VERY important; executing a while loop without
- it will cause an infinite loop and possibly crash the program. */
- var n = 0;
- while (n < 3) {
- console.log("Beatlejuice");
- n += 1; // super important to remember
- }
- /* A for in loop does for objects what the for loop does for an array--it iterates over the
- object's enumerable properties and performs an action at every stop. */
- var obj = {
- a: 1,
- b: 2,
- c: 3
- };
- for (var key in obj) {
- console.log(key + ": " + obj[key]);
- }
- /* Since objects are innately unsorted and looping through in a particular order can't be guaranteed,
- to get closer to looping in the order you wish, some external arranging must first take place.
- For example, using a regular for in loop may iterate through the key/values in the order they
- were assigned. To loop backwards, you could extract the keys and place them into an array,
- reverse the order of the array, and then use a for loop to iterate through the array and return
- a new object: */
- function reverseObj(object) {
- var newObj = {};
- var arr = Object.keys(object);
- arr.reverse(); // could also skip this line and iterate backwards in the for loop instead
- for (var i = 0; i < arr.length; i++) {
- newObj[arr[i]] = obj[arr[i]];
- // console.log(newObj); Uncomment me and you will see it insert the key/values in reverse
- }
- return newObj;
- }
- reverseObj(obj);
- /* Depending on which browser or program runs this code, it may still log it in the console
- in alphabetical order, but logging within the for loop displays the correct results. */
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