At underscore js, Can I get multiple columns with pluck method after input where method as linq select projection

Question

var people = [     {firstName : "Thein", city : "ny", qty : 5},     {firstName : "Michael", city : "ny", qty : 3},     {firstName : "Bloom", city : "nj", qty : 10} ];  var results=_.pluck(_.where(people, {city : "ny"}), 'firstName'); 

For example : I need firstName and qty.

Answer 1

To project to multiple properties, you need map, not pluck:

var results = _.map(     _.where(people, {city : "ny"}),      function(person) {         return { firstName: person.firstName, qty: person.qty };     } ); 

[{"firstName":"Thein","qty":5},{"firstName":"Michael","qty":3}]

(Fiddle)

Note that, if you wanted to, you could create a helper method "pluckMany" that does the same thing as pluck with variable arguments:

// first argument is the source array, followed by one or more property names var pluckMany = function() {     // get the property names to pluck     var source = arguments[0];     var propertiesToPluck = _.rest(arguments, 1);     return _.map(source, function(item) {         var obj = {};         _.each(propertiesToPluck, function(property) {             obj[property] = item[property];          });         return obj;     }); }; 

You can use the _.mixin function to add a "pluckMany" function to the _ namespace. Using this you can write simply:

var results = _.chain(people).where({city : "ny"}).pluckMany( "firstName", "qty").value(); 

(Fiddle)