Wrap all occurences of Array<word> in string in <em></em> Javascript, allowing &qu-CodePudding

The usecase: I have a search input that allows users to enter space-separated words to search for in a list of entries. I want to only display matches that match any of the words provided, and highlight those parts of the entries that match.

Given this array of haystacks:

const haystacks = [
 { value: 'Hello World', visible: true }, 
 { value: 'I was here', visible: true }, 
 { value: 'tell me your name', visible: true }
];

and this array of needles

const needles = ['el', 'rl', 'em'];

how can I wrap all matching parts of the strings in <em></em>, and for those that have no match set visible: false:

// expected result
[
  { value: 'H<em>el</em>lo Wo<em>rl</em>d', visible: true }, 
  { value: 'I was here', visible: false }, 
  { value: 't<em>el</em>l me your name', visible: true }
]

I have checked How to compare string with array of words and highlight words in string that match? but that one only highlights words that fully comply with the needles, not partial matches.

Here's what I've tried, which gives me

[
  { value: "H<<em>em</em>>el</<em>em</em>>lo Wo<<em>em</em>>rl</<em>em</em>>d", visible: true },
  { value: "I was here", visible: false },
  { value: "t<<em>em</em>>el</<em>em</em>>l th<em>em</em> your name",    "visible": true }
]

const haystacks = [{ value: 'Hello World', visible: true }, { value: 'I was here', visible: true }, { value: 'tell them your name', visible: true }];

const needles = ['el', 'rl', 'em'];

for (const haystack of haystacks) {
  for (const needle of needles) {
    const isMatchingOption = haystack.value.toLowerCase().includes(needle);
    haystack.visible = isMatchingOption;
    if (isMatchingOption) {
      const re = new RegExp(needle.replace(/([.?* ^$[\]\\(){}|-])/g, '\\$1'), 'gi');
      haystack.value = haystack.value.replace(re, '<em>$&</em>');
    }
  }
}

console.log(haystacks);

CodePudding user response：

You should aim to create only one, comprehensive regular expression, not one per needle:

const regEscape = s => s.replace(/[.* ?^${}()|[\\]/g, "\\$&");

function highlight(haystacks, needles) {
    // Sort needles by descending length (in a copy)
    needles = [...needles].sort((a, b) => b.length - a.length);
    const regex = RegExp(needles.map(regEscape).join("|"), "gi");
    return haystacks.map(({value}) => ({
       value: value.replace(regex, `<em>$&</em>`),
       visible: regex.test(value)
    }));
}

// Example run:
const haystacks = [
    { value: 'Hello World' }, 
    { value: 'I was here' }, 
    { value: 'tell me your name' }
];

const needles = ['el', 'rl', 'em'];

console.log(highlight(haystacks, needles));

The needles are sorted by descending length so that if one is a substring of the other, the longer one gets precedence for the replacement.