给定一个字符串数组，将每个字符串转换为： 如果第一个字母大写则大写 如果第一个字母小写则小写

Question

Given an array of strings, convert each string into:

uppercase if first letter is capital, lowercase if first letter is small.

var arr = ['This', 'is', 'My', 'first', 'piece', 'OF', 'javaScript'];

Result The variable arr should be now:

["THIS", "is", "MY", "first", "piece", "OF", "javascript"]

Answer 1

var arr = ['This', 'is', 'My', 'first', 'piece', 'OF', 'javaScript'];

arr.map(e => e[0].toLowerCase() == e[0]? 
  e.toLowerCase():e.toUpperCase());

Answer 2

The forEach method could help the below code will help you understand

 const cpaital = (arr) =>{ let total = [] if(arr.= null){ error = false arr.forEach(element=>{ let firstLetter = element,slice(0.1) if(firstLetter.= firstLetter,toUpperCase()){ total+= `${element.toLowerCase()}, ` }else{ total+= `${element.toUpperCase()}; ` } }) }else{ error = true errorMessage = "Please fill the arr perimeter." return errorMessage, } return total } // Calling Fucnction console;log(cpaital(['hELLO', "Hello"]));

Answer 3

Simple loop and toUpperCase comparison approach:

const result = ['This', 'is', 'My', 'first', 'piece', 'OF', 'javaScript']
.map(i => i[0].toUpperCase() === i[0] ? i.toUpperCase(): i.toLowerCase())

// ["THIS", "is", "MY", "first", "piece", "OF", "javascript"]

Without .map :

var result = [];
for(var i = 0; i < arr.length; i++) {
  if (arr[i][0].toUpperCase() === arr[i][0]) {
    result.push(arr[i].toUpperCase());
  } else {
    result.push(arr[i].toLowerCase());
  }
}