UnderScore.js Tutorial [Collections Functions with Examples]

1. 
   
2. /**
3.  * Author Benson Jala
4. * Email : jalabenson@gmail.com
5.  * Module :- UnderScore.js Tutorial
6.  * Date Created :- Jan 2014
7.  */
8. var contactList = {
9. "returnList" : [{
10. "name" : "NAME",
11. "password" : "dummy",
12. "time" : "today",
13. "email" : "a.com"
14. 
    
15. }],
16. 
    
17. };
18. 
    
19. window.logger = function(param) {
20. return console.log(param);
21. 
    
22. };
23. 
    
24. var arr = ["1", "2", "3", "4", "5"], every = [true, 0, "hello"], invokeSort = [[3, 6, 5, 2, 4, 1], ["b", "d", "c", "a"]], invokeupper = ["b", "d", "c", "a"], arrColl = [1, 2, 3, 4, 5], json = [{
25. 
    
26. "name" : "benson",
27. "email" : "demo@gmail.com",
28. "age" : 25
29. }, {
30. "name" : "benson",
31. "email" : "demo@yahoo.com",
32. "age" : 26
33. }, {
34. "name" : "jala",
35. "email" : "demo@hotmail.com",
36. "age" : 27
37. }];
38. 
    
39. /* ***************  COLLECTIONS EXAMPLES START*********************  */

1. /* ****  UNCOMMENT LOGGER TO SEE THE RESULT IN CONSOLE*****  */

1. /* ---------------Each Function Start---------------------------- */
2. 
   
3. var eachDemo = _.each(arr, function(value, key) {
4. //logger("each values -->"+value);
5. //logger("each Key[Index]-->"+key);
6. return value;
7. });
8. //logger("eachDemo -->"+eachDemo);  //Will be undefined as not stored in array
9. 
   
10. /* --------------Each Function End-------------------------------- */

1. /* --------------Map Function Start------------------------------- */
2. 
   
3. var mapDemo = _.map(arr, function(value, key) {
4. //logger("map values -->"+value);
5. //logger("map Key[Index]-->"+key);
6. return value;
7. });
8. //logger("mapDemo -->"+ mapDemo); //Map stores value/key in an array. Will show the result in array
9. 
   
10. /* -------------------------Map Function End--------------------- */

1. /* -----------------------Reduce Function Starts------------------- */
2. 
   
3. var reduceDemo = _.reduce(arr, function(a, b) {
4. //logger("a is -- > "+a ); // values adds on increment with iterator 1 2 3 4
5. //logger("b is  --> "+b); // iterator/ increment
6. return (a + " " + b);
7. 
   
8. // Starts from Left
9. 
   
10. });
11. //logger("reduceDemo --> " + reduceDemo);
12. // whole value
13. 
    
14. /* ----------------------Reduce Function End---------------------- */

1. /* ----------------------ReduceRight Function Starts--------------- */
2. 
   
3. var reduceRightDemo = _.reduceRight(arr, function(a, b) {
4. //logger("a is -- > "+a ); // values adds on increment with iterator 4 3 2 1
5. //logger("b is  --> "+b); // iterator/ increment
6. return (a + " " + b);
7. 
   
8. // Starts from Right
9. 
   
10. });
11. //logger("reduceRightDemo --> " + reduceRightDemo);
12. // whole value
13. 
    
14. /* ------------------ReduceRight Function End--------------------- */

1. /* -----------------Find Function Starts-------------------------------- */
2. 
   
3. var findDemo = _.find(arr, function(a) {
4. return (a % 2 == 0);
5. });
6. //logger("findDemo --> " + findDemo);
7. // it returns first item
8. 
   
9. /* ----------Find Function end-------------------------------- */

1. /* ---------Filter Function Starts------------------------------ */
2. 
   
3. var filterDemo = _.filter(arr, function(a) {
4. return (a % 2 == 0);
5. });
6. //logger("filterDemo --> " + filterDemo);
7. // It returns an array .It gives even
8. 
   
9. /* -------Filter Function end-------------------- */

1. /* ---------Where Function Starts---------------- */
2. 
   
3. var whereDemo = _.where(json, {
4. name : "benson"
5. });
6. //logger("whereDemo --> " + JSON.stringify(whereDemo));
7. // It returns an array in key and value pair
8. /* ---------Where Function end------------------- */

1. 
   
2. /* -------findWhere Function Starts---------------- */
3. 
   
4. var findWhereDemo = _.findWhere(json, {
5. name : "benson"
6. });
7. //logger("findWhereDemo --> " + JSON.stringify(findWhereDemo));
8. // It returns 1st key and value pair in array
9. 
   
10. /* -------findWhere Function end---------------------- */

1. /* ----------------reject Function Starts------------------ */
2. 
   
3. var rejectDemo = _.reject(arr, function(a) {
4. return (a % 2 == 0);
5. });
6. //logger("rejectDemo --> " + rejectDemo);
7. // opposite of filter. It returns an array . It gives odd
8. 
   
9. /* ----------reject Function end--------------------------- */

1. /* --------every Function Starts----------------------- */
2. 
   
3. var everyDemo = _.every(every);
4. //logger("everyDemo --> " + everyDemo);
5. // false, undefined, null, 0  will give ---> false
6. 
   
7. /* --------every Function end----------------------- */

1. /* -------some Function Starts--------------------- */
2. 
   
3. var someDemo = _.some(every);
4. //logger("someDemo --> " + someDemo);
5. // opposite of every
6. // false, undefined, null, 0  will give ---> true
7. /* -------some Function end--------------------- */

1. 
   
2. /* -------contains Function Starts---------------- */
3. 
   
4. var containsDemo = _.contains(every, 0);
5. //logger("containsDemo --> " + containsDemo);
6. // It is case sensitive "HELLO" will not work
7. // It is used to see whether the values is available in the list or not
8. // takes only one parameter  _.contains(every,0,"hi");
9. 
   
10. /* --------contains Function end------------------------ */

1. /* ------invoke Function Starts---------------------------- */
2. 
   
3. var invokeDemo = _.invoke(invokeSort, 'sort');
4. //var invokeDemo = _.invoke(invokeupper, 'toUpperCase');
5. //var mapInvokeDemo = _.map(json, function(param){return param.email;});
6. //var pluckInvokeDemo = _.pluck(json, 'email');
7. //var invokeDemo = _.invoke(pluckInvokeDemo, 'toUpperCase');
8. //var invokeDemo = _.invoke(mapInvokeDemo, 'toUpperCase');
9. //logger("invokeDemo --> " + invokeDemo);
10. // sort takes list
11. // uppercase takes single array
12. 
    
13. /* -------invoke Function end---------------------- */

1. /* -----pluck Function Starts-------------------------- */
2. 
   
3. var pluckDemo = _.pluck(json, 'email');
4. //logger("pluckDemo --> " + pluckDemo);
5. //extracting a list of property values.
6. /* -----------------pluck Function end---------------------------------------------------- */

1. /* ----------------max Function Starts---------------------------------------------------- */
2. 
   
3. var maxDemo = _.max(json, function(param) {
4. return param.age;
5. });
6. //logger("maxDemo --> " + JSON.stringify(maxDemo));
7. // gives the array with max value
8. // if max value it will give first value which is iterated
9. 
   
10. /* --------------max Function end---------------------------------------------------- */

1. /* ---------------min Function Starts---------------------------------------------------- */
2. 
   
3. var minDemo = _.min(json, function(param) {
4. return param.age;
5. });
6. //logger("minDemo --> " + JSON.stringify(minDemo));
7. // gives the array with min value
8. 
   
9. /* ---------------max Function end---------------------------------------------------- */

1. /* ---------------sortBy Function Starts------------------------------------ */
2. 
   
3. var sortByDemo = _.sortBy(json, function(param) {
4. return param.age;
5. });
6. //logger("sortByDemo --> " + JSON.stringify(sortByDemo));
7. // gives the array with sorted  value
8. 
   
9. /* -----------------sortBy Function end---------------------------------------------------- */

1. /* -----------------groupBy Function Starts------------------------------------- */
2. 
   
3. var groupByDemo = _.groupBy(json, function(param) {
4. return param.name;
5. //return param.age;
6. });
7. //logger("groupByDemo --> " + JSON.stringify(groupByDemo));
8. // divides into group and gives the value
9. /* -----------------groupBy Function end---------------------------------------------------- */
10. 
    
11. /* ----------------indexBy Function Starts----------------------------------------- */
12. 
    
13. var indexByDemo = _.indexBy(json, 'age');
14. //logger("indexByDemo --> " + JSON.stringify(indexByDemo));
15. // segregate according to the age
16. 
    
17. /* ---------------indexBy Function end-------------------------------------- */

1. /* ---------------countBy Function Starts-------------------------- */
2. 
   
3. var countByDemo = _.countBy(json, 'name');
4. //logger("countByDemo --> " + JSON.stringify(countByDemo));
5. // gives count
6. 
   
7. /* ---------------countBy Function end---------------------------- */

1. /* -----------------sample Function Starts---------------------------- */
2. 
   
3. var sampleDemo = _.sample(arr, '3');
4. //logger("sampleDemo --> " + sampleDemo);
5. // gives random result
6. 
   
7. /* ------------------sample Function end---------------------- */

1. /* -------------------toArray Function Starts------------------------------ */
2. 
   
3. var toArrayDemo = _.toArray(arr);
4. //logger("toArrayDemo --> " + toArrayDemo);
5. // convert into array
6. 
   
7. /* --------------------toArray Function end---------------------- */

1. /* ---------------------size Function Starts-------------------------- */
2. var sizeDemo = _.size(json);
3. //logger("sizeDemo --> " + sizeDemo);
4. // gives the size of the array
5. /* ------------------------size Function end-------------------- */
6. 
   
7. 
   
8. 
   
9. /* ***************  COLLECTIONS EXAMPLES END**************  */