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javascriptregexdo-loops

Can anyone please explain this piece of code?

do{    
         var string1=prompt("Enter text");     
} while(!string1||!/^[a-zA-Z\s]*$/.test(string1));

Can someone please explain to me the condition inside while in detail?

Solution

  • !string will be true if the string is not empty, meaning string !== '' && string !== null && string !== false && string !== undefined

    The regular expression /^[a-zA-Z\s]*$/ matches any string that only contains a letter/whitespace and by doing ! we want the oppossite. A string that contains at least one character that it is not a letter/whitespace

    enter image description here

    The .test method evaluates a regular expression against a given string, and will return true if the pattern matches the string.

    So:

    '333' // true
' 333' // true
'aaa' // false
'   ' // false
'3a3' // true


    const arr = [
  '333', // I have at least 1 non letter/whitespace
  '444', // I have at least 1 non letter/whitespace
  ' 44', // I have at least 1 non letter/whitespace
  'a$', // I have at least 1 non letter/whitespace
  'aaaa', // false
  'ZZZ', // false
  '   ', // false
  '"$a%' // I have at least 1 non letter/whitespace
];

arr.forEach(string => {
  console.log(`${string}: ${!/^[a-zA-Z\s]*$/.test(string)}`);
});