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algorithm: count letters (TheAlgorithms#1164)

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	`1`	`+/**`
	`2`	`+ *@function countLetters`
	`3`	`+ *@description Given a string, count the number of each letter.`
	`4`	`+ *@param {String} str - The input string`
	`5`	`+ *@return {Object} - Object with letters and number of times`
	`6`	`+ *@example countLetters("hello") => {h: 1, e: 1, l: 2, o: 1}`
	`7`	`+ */`
	`8`	`+`
	`9`	`+constcountLetters=(str)=>{`
	`10`	`+constspecialChars=/\W/g`
	`11`	`+`
	`12`	`+if(typeofstr!=='string'){`
	`13`	`+thrownewTypeError('Input should be a string')`
	`14`	`+}`
	`15`	`+`
	`16`	`+if(specialChars.test(str)){`
	`17`	`+thrownewTypeError('Input must not contain special characters')`
	`18`	`+}`
	`19`	`+`
	`20`	`+if(/\d/.test(str)){`
	`21`	`+thrownewTypeError('Input must not contain numbers')`
	`22`	`+}`
	`23`	`+`
	`24`	`+constobj={}`
	`25`	`+for(leti=0;i<str.toLowerCase().length;i++){`
	`26`	`+constchar=str.toLowerCase().charAt(i)`
	`27`	`+obj[char]=(obj[char]\|\|0)+1`
	`28`	`+}`
	`29`	`+`
	`30`	`+returnobj`
	`31`	`+}`
	`32`	`+`
	`33`	`+export{countLetters}`

Lines changed: 33 additions & 0 deletions

Original file line number	Diff line number	Diff line change
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	`1`	`+import{countLetters}from'../CountLetters'`
	`2`	`+`
	`3`	`+describe('CountLetters',()=>{`
	`4`	`+it('expect throws on use wrong param',()=>{`
	`5`	`+expect(()=>countLetters(0)).toThrow()`
	`6`	`+})`
	`7`	`+`
	`8`	`+it('expect throws when using a number in the string',()=>{`
	`9`	`+expect(()=>countLetters('h3llo')).toThrow()`
	`10`	`+})`
	`11`	`+`
	`12`	`+it('expect throws when using a special characters in the string',()=>{`
	`13`	`+expect(()=>countLetters('hello!')).toThrow()`
	`14`	`+})`
	`15`	`+`
	`16`	`+it('count the letters in a string. Allows lower case',()=>{`
	`17`	`+constvalue='hello'`
	`18`	`+constcount=countLetters(value)`
	`19`	`+expect(count).toEqual({h:1,e:1,l:2,o:1})`
	`20`	`+})`
	`21`	`+`
	`22`	`+it('count the letters in a string. Allows upper case',()=>{`
	`23`	`+constvalue='HELLO'`
	`24`	`+constcount=countLetters(value)`
	`25`	`+expect(count).toEqual({h:1,e:1,l:2,o:1})`
	`26`	`+})`
	`27`	`+`
	`28`	`+it('count the letters in a string. Allows upper and lower case',()=>{`
	`29`	`+constvalue='HelLo'`
	`30`	`+constcount=countLetters(value)`
	`31`	`+expect(count).toEqual({h:1,e:1,l:2,o:1})`
	`32`	`+})`
	`33`	`+})`

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