- Filtering a list to transform the elements we want to get back<\/li><\/ul>\n\n\n\n
var numbers = _.range(0,10); \/\/ [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n\nvar evenNumbers = _.filter(numbers, function(e){ return e % 2 != 0; });\n\/\/ evenNumbers is now [ 0, 2, 4, 6, 8 ]\n<\/code><\/pre>\n\n\n\n<\/a>Reduce<\/h3>\n\n\n\n
- Reducing a list of objects to a single value.<\/li>
- Ex=>A group of people can buy a meal or not. In that case we have to check out they have the enough amount by the sum of money they have.<\/li>
- (Each’s money => sum money)<\/li><\/ul>\n\n\n\n
var ppl = [\n {\n 'name': 'Keita',\n 'money': 1000\n },\n {\n 'name': 'Sato',\n 'money': 3000\n },\n {\n 'name': 'Ruma',\n 'money': 500\n },\n]\n\nvar sumMoney = function(data){\n return _.reduce(\n data,\n function(accumulated, e){\n return accumulated + e.money;\n },\n 0\n );\n}\n\nfunction canBuyMeal(data){\n return 3500 < sumMoney(data);\n}\n\ncanBuyMeal(ppl); \/\/ returns true\n<\/code><\/pre>\n\n\n\n<\/a>Some<\/h3>\n\n\n\n
- If there is at least one record in a collection that meets some criteria.<\/li><\/ul>\n\n\n\n
var ppl = [\n {\n 'name': 'Keita',\n 'hasMoney': true\n },\n {\n 'name': 'Sato',\n 'hasMoney': false\n },\n {\n 'name': 'Ruma',\n 'hasProperty': true\n },\n]\n\nfunction canLive(data){\n return _.some(data, function(e){ return e.hasProperty; });\n}\n\ncanGroupDrive(ppl); \/\/ returns true\n<\/code><\/pre>\n\n\n\n<\/a>Map<\/h3>\n\n\n\n
- Useful for changing a list into a different list in a purely declarative way.<\/li>
- Can just specify how you want to manipulate an element of a list.<\/li>
- Make a new list transformed by providing a function<\/li><\/ul>\n\n\n\n
var res1 = _.range(5); \/\/ [ 0, 1, 2, 3, 4]\n\nvar res2 = _.map(a, function(e){ return e + e;} );\n\n\/\/result is [0, 2, 4, 6, 8]<\/code><\/pre>\n\n\n\nBy Yuuma<\/p>\n
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- If there is at least one record in a collection that meets some criteria.<\/li><\/ul>\n\n\n\n
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