JavaScript Experiment Collection

function getKeysOfObject() {
    let o = {'a': 1, 'b': function() {}, 'c': 2}; 
    console.log(Object.keys(o));
}
getKeysOfObject();
Result:["a", "b", "c"]
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function addPropertyToObj() {
    let o = {};
    o['a'] = 87;
    console.log(o);
}
addPropertyToObj();
Result: {a: 87}
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function processStringWithMap() {
    let str = 'hello';
    let map = Array.prototype.map;
    let a = map.call(str, function(e) { return e.concat('N')});
    console.log(a);
}
processStringWithMap();
Result: ["hN", "eN", "lN", "lN", "oN"]
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function calculateSumOfNumberArray() {
   let total = [1,2,3].reduce((accumulator, currentValue)=> {return accumulator + currentValue});
   console.log(total);
}
calculateSumOfNumberArray();
Result: 6
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function calculateSumOfObjectArray() {
   let total = [{x:1},{x:2},{x:3}].reduce((accumulator, currentValue) => {return accumulator + currentValue.x},0);
   console.log(total);
}
calculateSumOfObjectArray();
Result: 6
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function flattenArray() {
  let newArray = [[0,1],[2,3],[4,5]].reduce((accumulator, currentValue)=> {return accumulator.concat(currentValue)},[]);
  console.log(newArray);
}
flattenArray();
Result: [0,1,2,3,4,5]
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function countInstancesOfValuesOfArrayInObject() {
  let names = ['Alice', 'Bob', 'Tiff', 'Bob', 'Alice'];
  let countedNames = names.reduce((allNames, name)=> { 
      if(name in allNames) {
        allNames[name]++;
      } else {
        allNames[name] = 1;
      }
      return allNames;
  },{})
  console.log(countedNames);
}
countInstancesOfValuesOfArrayInObject();
Result: {Alice: 2, Bob: 2, Tiff: 1}
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function groupBy(objectArray, property) {
  return objectArray.reduce(function (acc, obj) {
    let key = obj[property]
    if (!acc[key]) {
      acc[key] = []
    }
    acc[key].push(obj)
    return acc
  }, {})
}

function applyGroup() {
    let people = [
      { name: 'Alice', age: 21 },
      { name: 'Max', age: 20 },
      { name: 'Jane', age: 20 }
    ];
    let groupedPeople = groupBy(people, 'age');
    console.log(groupedPeople);
}
applyGroup();
Result:
{ 
    20: [
     { name: 'Max', age: 20 }, 
     { name: 'Jane', age: 20 }
    ], 
    21: [{ name: 'Alice', age: 21 }] 
}
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function removeDuplicatedItem() {
  let myArray = ['a', 'b', 'a', 'b', 'c', 'e', 'e', 'c', 'd', 'd', 'd', 'd'];
  let myOrderedArray  = myArray.reduce((accumulator, currentValue)=>{
    if (accumulator.indexOf(currentValue) === -1) {
        accumulator.push(currentValue)
    }
    return accumulator
  },[]);
  return myOrderedArray;
}
removeDuplicatedItem();
Result: ["a", "b", "c", "e", "d"]