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Jessica7/resumo.js

Created August 31, 2016 00:44
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resumo Array
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resumo.js
// ESTUTURA DE DADOS com JavaScript
// ******{ VETORES/ARRAYS }********
//JavaScript arrays are objects
// create Array
var numbers = [];
// you have an array with length of 0
console.log(numbers.length);
// set values
var numbers = [1,2,3,4,5];
print(numbers.length); // displays 5
// Other form to create an array
var numbers = new Array();
console.log(numbers.length); // displays 0
// setting elements
var numbers = new Array(1,2,3,4,5);
console.log(numbers.length); // displays 5
// create an array constructor with single argument specifying the length of the array
var numbers = new Array(10);
console.log(numbers.length); // displays 10
// JavaScript array elements do not all have to be of the same type
var objects = [1, "Joe", true, null];
// verify if object is an array with Array.isArray() function
var numbers = 3;
var arr = [7,4,1776];
console.log(Array.isArray(numbers)); // displays false
console.log(Array.isArray(arr)); // displays true
// PS: the most JavaScript experts recommend using the [] operator, saying it is more efficient than Array constructor
//Acessing and writing Array elements
// Data is assigned to array elements using the [] operator in an assignment statement.
// For example, the following loop assigns the values 1 through 100 to an array:
var nums = [];
for (var i = 0; i < 10; ++i) {
nums[i] = i+1;
}
//Array elements are also accessed using the [] operator. For example:
var numbers = [1,2,3,4,5];
var sum = numbers[0] + numbers[1] + numbers[2] + numbers[3] +
numbers[4];
console.log(sum);
//accessing all the elements of an array sequentially is much easier using a for loop
var numbers = [1,2,3,5,8,13,21];
var sum = 0;
for (var i = 0; i < numbers.length; ++i) {
sum += numbers[i];
}
console.log(sum); // displays 53
// Creating Arrays from Strings
// split()
//This function breaks up a string at a common delimiter, such as a space for each word, and
//creates an array consisting of the individual parts of the string
var sentence = "the quick brown fox jumped over the lazy dog";
var words = sentence.split(" ");
for (var i = 0; i < words.length; ++i) {
console.log("word " + i + ": " + words[i]);
}
// Aggregate Array Operations
//There are several aggregate operations you can perform on arrays
// First, you can assign one array to another array
var nums = [];
var samenums = []
for (var i = 0; i < 10; ++i) {
nums[i] = i+1;
}
var samenums = nums;
// However, when you assign one array to another array, you are assigning a reference to the assigned array
// When you make a change to the original array, that change is reflected in the other array as well
var nums = [];
for (var i = 0; i < 100; ++i) {
nums[i] = i+1;
}
var samenums = nums;
nums[0] = 400;
console.log(samenums[0]); // This is called a shallow copy.
// The new array simply points to the original array’s elements.
// (o novo array aponta para o array original)
// A better alternative is to make a deep copy, so that each of the original array’s elements
// is actually copied to the new array’s elements
function copy(arr1, arr2) {
for (var i = 0; i < arr1.length; ++i) {
arr2[i] = arr1[i];
}
}
var nums = [];
for (var i = 0; i < 10; ++i) {
nums[i] = i+1;
}
var samenums = [];
copy(nums, samenums);
nums[0] = 400;
console.log(samenums[0]);// displays 1
var nums = [1,2,3,4,5];
console.log(nums);// 1, 2 , 3 ,4 5
//Accessor Functions
//functions you can use to access the elements of an array
//Searching for a Value
// *indexOf()
//the function returns the index position of the argument
//If the argument is not found in the array, the function returns -1
var names = ["David", "Cynthia", "Raymond", "Clayton", "Jennifer"];
var name = 'Jesica';
var position = names.indexOf(name);
if (position >= 0) {
console.log("Found " + name + " at position " + position);
}
else {
console.log(name + " not found in array." + position);
}
//PS: If you have multiple occurrences of the same data in an array, the indexOf() function
//will always return the position of the first occurrence
// * lastIndexOf()
//will return the position of the last occurrence of the argument in the array, or -1
//if the argument isn’t found
var names = ["David", "Mike", "Cynthia", "Raymond", "Clayton", "Mike","Jennifer"];
var name = "Mike";
var firstPos = names.indexOf(name);
console.log("First found " + name + " at position " + firstPos); // First found Mike at position 1
var lastPos = names.lastIndexOf(name);
console.log("Last found " + name + " at position " + lastPos); // Last found Mike at position 5
//String Representations of Arrays
// * join() and toString()
//Both functions return a string containing the elements of the array de‐
//limited by commas.
var names = ["David", "Cynthia", "Raymond", "Clayton", "Mike", "Jennifer"];
var namestr = names.join();
console.log(namestr); // David,Cynthia,Raymond,Clayton,Mike,Jennifer
namestr = names.toString();
console.log(namestr); // David,Cynthia,Raymond,Clayton,Mike,Jennifer
//Creating New Arrays from Existing Arrays
//There are two accessor functions that allow you create new arrays from existing arrays
// * concat() and splice() .
// Concat() - The concat() function allows you to put together two or more arrays to create a new array
// * concat()
var cisDept = ["Mike", "Clayton", "Terrill", "Danny", "Jennifer"];
var dmpDept = ["Raymond", "Cynthia", "Bryan"];
var itDiv = cisDept.concat(dmpDept);
console.log(itDiv);
// * Splice()
var itDiv = ["Mike","Clayton","Terrill","Raymond","Cynthia","Danny","Jennifer"];
var dmpDept = itDiv.splice(3,3);
var cisDept = itDiv;
console.log(dmpDept); // Raymond,Cynthia,Danny
console.log(cisDept); // Mike,Clayton,Terrill,Jennifer
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