使用 for 循环替换子字符串

Question

I'm trying to replace a substring with the word 'denied'. For example: if the original string is "abcdefg" and sub-string to replace is "bcd", expected output is "a DENIED efg".

I can't use .replace or anything else, just .substring

function replacer (variable, replace) {
    for (let a = variable.length - 1; a >=0; a--) {
        for (let b = replace.length - 1; b >= 0; b--) {
            if (replace[b] === variable[a]) {
                   
            }
        }
    }
}

I have no clue what to do next.

Here is my code to just remove characters from a string.

let stringToReturn = original;
  for (let a = toDelete.length - 1; a >= 0; a--) {
    for (let b = original.length - 1; b >= 0; b--) {
      if (original[b] === toDelete[a]) {
           stringToReturn = stringToReturn.substring(0, b) + stringToReturn.substring(b + 1, stringToReturn.length);   
          } else {
           continue;
      }
    }
  }
alert(stringToReturn);
}

But this time I need not to just remove one characters, but find a sub-string to replace with DENIED . I apologize for the code style.

Answer 1

If you know the length of the substring you're trying to replace, then you can just iterate the string and examine all possible substrings of this length, as you were looking through a "window":

 function replace(full, partial, placeholder) { for (let i = 0; i <= full.length - partial.length; i++) { const current = full.substring(i, i + partial.length); if (current === partial) { const prefix = full.substring(0, i); const suffix = full.substring(i + partial.length); return `${prefix}${placeholder}${suffix}`; } } } const ans = replace('abcdefghij', 'def', 'DENIED'); console.log(ans);

If you want to replace all occurrences, just don't return the value after the first match:

 function replaceAll(full, partial, placeholder) { let tmp = full; for (let i = 0; i <= tmp.length - partial.length; i++) { const current = tmp.substring(i, i + partial.length); if (current === partial) { const prefix = tmp.substring(0, i); const suffix = tmp.substring(i + partial.length); tmp = `${prefix}${placeholder}${suffix}`; i += placeholder.length; } } return tmp; } const ans = replaceAll('abcdefghijdef', 'def', 'DENIED'); console.log(ans);

Answer 2

const source = "abcdefg";
const target = "bcd";
const replacer = "DENIED";



const replace = (source, target, replacer) => {
  const position = source.indexOf(target);
  if(position === -1) return source;
  let output = source.substr(0, position)
  output += replacer
  output += source.substr(position + target.length);
  return output
}

const replaceAll = (source, target, replacer) => {
     let output = source;
     do{
       output = replace(output, target, replacer)
     }
     while(output !== replace(output, target, replacer))
     return output;
}

console.log(replace(source, target, replacer))

and for sure best solution, easiest to understand, clean and elegant is :

const replaceAll = (source, target, replacer) => {
  return source.split(target).join(replacer)
}

Answer 3

Since you didn't specify whether you want to do a full replace or a singular, I've modified this to allow for a boolean parameter, this boolean says whether to do a singular or full replace.

 const replaceword = "DENIED"; const testword = "abcdef"; const testword2 = "abcdefdexyz"; const testword3 = "hello I don't have the sub"; //function takes a word parameter - the word to do a replace on //and sub parameter of what to replace //and replacement parameter of what to replace the substring with //replaceall is a boolean as to whether to do a full replace or singular function replace(word, sub, replacement, replaceall){ replaceall = replaceall || false; //default to singular replace //Get the first index of the sub to replace const startOfReplace = word.indexOf(sub); //get the ending index of where the substring to be replaced ends const endOfReplace = startOfReplace + sub.length - 1; //variable to hold new word after replace let replacedWord = ""; //If the substring is found do the replacement with the given replacement word if(startOfReplace > -1){ for(let i = 0; i < word.length; i++){ if(i == startOfReplace){ replacedWord += replacement; }else if(i >= startOfReplace && i <= endOfReplace){ continue; }else{ replacedWord += word[i]; } } }else{ //set the return to the passed in word as no replacement can be done replacedWord = word; return replacedWord; } if(replaceall) //if boolean is true, recursively call function to replace all occurrences //recursive call if the word has the sub more than once return replace(replacedWord, sub, replacement); else return replacedWord; //else do the singular replacement } console.log(replace(testword, "de", replaceword)); console.log(replace(testword2, "de", replaceword, true)); console.log(replace(testword3, "de", replaceword));