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reverseString.js
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256 lines (167 loc) · 10.2 KB
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"use strict";
// OBJECTIVE ////////////////////////////////////////////////////////////////////////////////////////////////
// Given a string, return a new string with a reversed order of characters.
// -- Examples: reverse('hello') => 'olleh'
// SUMMARY //////////////////////////////////////////////////////////////////////////////////////////////////
// What is the problem?:
// You need to take a string and reverse it.
// What is the BEST solution?
// 1. Solution 2 (and by extension solution 1) is the most preferable way since its short, simple, and concise.
// 2. Solution 5 uses the array spread operator which simplifies the process a great deal.
// 3. Solutions 3 and 4 are more cumbersome but loops are helpful to use.
// What are the special components of these solutions?:
// 1. solutions 1 & 2 -- general scripting strategies (see **funstru** for structural examples).
// 2. solutions 3 & 4 -- loops (loops over the block of code until a certain condition is true).
// 3. solutions 5 -- uses array spread operator (i.e. pushes all items into an array).
// 4. solution 6 -- uses .reduce() method (i.e. have a rray of amounts and want to add them all up).
// 5. solution 7 -- same as solution 5, but uses es6 fat arrow function instead.
// 6. solution 8 -- same as solution 6, but uses cleaner code.
// What needs work?
// 1. Add commentary to solution 6 and 7.
//////////////////////////////////////////////////////////////////////////// //////////////////////////////////
///// SOLUTIONS ///////////////////////////////////////////////////////
///// Solution 1: BUILT-IN METHODS:
function reverseString1(string) {
const array = string.split('');
array.reverse();
return array.join('')
}
///// Solution 2: CHAINING METHODS TOGETHER:
function reverseString2(string) {
return string.split('').reverse().join('');
}
///// Solution 3: DECREMENTING LOOP:
function reverseString3(string) {
let newString = '';
for (let i = string.length - 1; i >= 0; i-- ) {
newString += string[i];
}
return newString;
}
/////// Solution 4: For... of Loop:
function reverseString4(string) {
let reversed = '';
for (let character of string) {
reversed = character + reversed;
}
return reversed;
}
/////// Solution 5: Array spread operator:
function reverseString5(string) {
return [...string].reverse().join('');
}
/////// Solution 6: Using a function:
function reverseString6(string) {
return string.split('').reduce(function (reversed, character) {
return character + reversed;
}, '');
}
/////// Solution 7: Using .reduce():
function reverseString7(string) {
return string.split('').reduce((reversed, character) => {
return character + reversed;
}, '');
}
///// Solution 8: Using a cleaner version with .reduce()
function reverseString8(string) {
return string.split('').reduce((reversed, character) => character + reversed, '');
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///// SOLUTIONS STEP-BY-STEP ////////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///// Solution 1: (comments):
function reverseString11(string) {
// Step 1: Use the split() method to return a new array, which results in ["h", "e", "l", "l", "o"].
const array = string.split('');
// Step 2: Use the reverse() method to reverse the new created array, which results in ["o", "l", "l", "e", "h"].
array.reverse();
// Step 3: Use the join() method to join all elements of the array into a string, which results in "olleh".
return array.join('')
}
///// Solution 2 (comments):
function reverseString22(string) {
// STEP 1: Take the argument (i.e. string) and simply chain the methods you want.
return string.split('').reverse().join('');
}
///// Solution 3 (comments):
function reverseString33(string) {
// STEP 1: Create an empty string that will host the new created string.
let newString = '';
// Step 2. Create the FOR loop
// The starting point of the loop will be (str.length - 1) which corresponds to the last character of the string, "o".
// As long as i is greater than or equals 0, the loop will go on.
// We decrement i after each iteration .
/* Here, hello's length equals 5.
For each iteration: i = str.length - 1 and newString = newString + str[i]
First iteration: i = 5 - 1 = 4, newString = "" + "o" = "o"
Second iteration: i = 4 - 1 = 3, newString = "o" + "l" = "ol"
Third iteration: i = 3 - 1 = 2, newString = "ol" + "l" = "oll"
Fourth iteration: i = 2 - 1 = 1, newString = "oll" + "e" = "olle"
Fifth iteration: i = 1 - 1 = 0, newString = "olle" + "h" = "olleh"
End of the FOR Loop*/
for (let i = string.length - 1; i >= 0; i-- ) {
newString + string[i];
}
// Step 3. Return the reversed string
return newString;
}
////// Solution 4 (comments):
function reverseString44(string) {
// STEP 1: Create a temporay variable called reverse and assign it an empty string.
// (This is the string that will be assembled over time as we iterate through the string).
let reversed = '';
// STEP 2: Using a for loop, we take each character out of the original string and stick it in a new one, one at a time.
// This is saying:
// 1. "for"...
// 2. Inside parentheses, create a temporary variable (i.e. "let character") that is redeclared every time through the loop.
// 3. "of"...
// 4. The iterable object we want to iterate through (i.e. "string") passed in as an argument.
for (let character of string) {
// STEP 3: In the body of the loop, we add "character" added on to the start of the string reversed.
reversed = character + reversed;
}
// STEP 4: After the entire for loop, we return "reversed".
return reversed;
}
///// SOLUTION 5 (comments):
function reverseString55(string) {
// using the array spread operator, takes the string, pushes it into an array, reverses it, then
// joins it back together as a string.
return [...string].reverse().join('');
}
///// SOLUTION 6 (comments):
function reverseString66(string) {
return string.split('').reduce(function (reversed, character) {
return character + reversed;
}, '');
}
///// SOLUTION 7 (comments):
function reverseString77(string) {
return string.split('').reduce((reversed, character) => {
return character + reversed;
}, '');
}
///// SOLUTION 8 /////////////////////////////////////////////////////
function reverseString88(string) {
// STEP 1: Turn the string into an array (by calling split function on it).
// STEP 2: Then use Reduce Helper.
// Reduce takes all the different values within an array and condense them down to a single string value.
// Reduce takes two seperate arguments, the arrow function and starting intial value for our function which is an empty string.
// STEP 3: Reduce will cycle through each number in the array (like a for loop).
// STEP 4:
return string.split('').reduce((reversed, character) => character + reversed, '');
}
// Reduce helper
// STEP 1: string.split turns this into an array,
// STEP 2: Then we set up the reduce helper function,
// Note on reduce: Reduce is used to take all the different values within an array and condense it down to one singular value.
// So what we're doing here is taking all the values in the array "string.split('')" and then condense (.reduce) to a single string value.
///// Output //////////////////////////////////////////////////////////
console.log(reverseString1("hello 1")); // 1 olleh
console.log(reverseString2("hello 2")); // 2 olleh
console.log(reverseString3("hello 3")); // 3 olleh
console.log(reverseString4("hello 4")); // 2 olleh
console.log(reverseString5("hello 5")); // 2 olleh
console.log(reverseString6("hello 6")); // 2 olleh
console.log(reverseString7("hello 7")); // 2 olleh
console.log(reverseString8("hello 8")); // 2 olleh