Regexp replace any single word-CodePudding

I need to replace 'page.a = b' with 'page.a = node.b'. In a word, i need to turn single word 'b' into 'node.b'; In other word, the string 'page.a = b && page.a < c' shold be transformed into 'page.a = node.b && page.a < node.c', just add 'node.' as the prefix to the single words. Can anyone help me with this? I think the js regexp can work but just cannot find the way with it.

let origin = 'page.a = b'
let expected = 'page.a = node.b';

How do i get the expected string from the origin ?

CodePudding user response：

You can use negative lookarounds to look for a word character that aren't preceded by or followed by a dot or another word character:

(?<![.\w])(\w)(?![.\w])

and replace the matching character with:

node.$1

https://regex101.com/r/GD2N9g/3

CodePudding user response：

You can try this approach:

Logic:

Split string using equals to(=) to get LHS and RHS as this operation only needs to be done on RHS.
Create a regex to match any word period combination. You can also use non-space characters(/[\s] /) as this will cover bracket notations and underscore as well
For each match, check if they do not have period(.) in it. If not, you can append prefix and return it.
Join both halves and return the string

let origin = 'page.a = b'
let o1 = 'page.a = b && page.a < c'

function transformStr(str, prefix) {
  const regex = /([\w.] )/g;
  const [lhs, rhs] = str.split('=')
  const newRhs = rhs.replace(regex, (part) => {
    return /^\w $/.test(part) ? `${prefix}.${part}` : part
  })
  return `${lhs}=${newRhs}`
}

console.log(transformStr(origin, 'node'))
console.log(transformStr(o1, 'node'))

As an extension, you can add support for special characters that can exists in a variable. This approach matches non-spaced character groups and processes only the ones that has only word characters or underscore or dollar

function transformStr(str, prefix) {
  const regex = /([^\s] )/g;
  const [lhs, rhs] = str.split('=')
  const newRhs = rhs.replace(regex, (part) => {
    return /^[\w\$] $/.test(part) ? `${prefix}.${part}` : part
  })
  return `${lhs}=${newRhs}`
}

console.log(transformStr('page.a = b', 'node'))
console.log(transformStr('page.a = b && page.a < c', 'node'))
console.log(transformStr('page._a = _b && page.a < $c', 'node'))