CODEWITHSUNDEEP
javascriptstringobjectreplace
Sergei Konovalov
Sergei Konovalov

Reputation: 23

How to replace string with object nested values

I've got interesting question. Imagine, we have a string like:

'i need this {client.car.model} exactly at {client.order.time} today'

How to replace such complex fields with object values? I don't know, how many levels: client.car.door.left... etc

Of course, i can extract this via regex in loop.

const re = /{(.+?)}/gi;

let regex = re.exec(s);

But after that - how to replace all fields & sub-fields?

Upvotes: 1

Views: 768

Answers (2)

samanime
samanime

Reputation: 26617

So, you've already correctly identified HOW to get the pattern, so your real question is "how can I take a string like 'client.order.time' and get a value for it?"

With a recursive function, it is surprisingly straightforward. Say we have an object like below:

const data = {
  client: {
    order: {
      time: '12:00PM'
    }
  }
};

We can create a function that takes an object and a string, and recursively loops through each part until it either a) gets through all the parts and finds the value or b) finds an unknown part and returns undefined.

const data = {
  client: {
    order: {
      time: '12:00PM'
    }
  }
};

const getValueFromPath = (obj, path, delimiter = '.') => {
  // path or obj are falsy, just return obj
  // you could tweak this bit to do something else if you want
  // obj === undefined might be from our recursive call, so keep that in mind if you tweak
  if (!path || !obj) return obj;

  const parts = path.split(delimiter);
  const next = parts.shift(); // get the first part, parts now has all the other parts
  
  // If !parts.length (parts.length === 0), we're on the last part, so we'll return.
  if (!parts.length) return obj[next];
  
  // Otherwise, recurse with the rest of the parts.
  return getValueFromPath(obj[next], parts.join(delimiter), delimiter);
};

const result = getValueFromPath(data, 'client.order.time');
console.log(result);

const noResult = getValueFromPath(data, 'path.does.not.exist');
console.log(noResult);

If you don't like re-join()-ing the parts every time, you could have a second version of this method which takes an array of parts instead of a path string, but I find the extra code isn't worth the (very minimal) efficiency gains.

Now, circling back to your original question, simply use the replace() method on the string, using a replacer method as the second argument. The 2nd argument of that replacer method is the pattern, so we just feed that to our new method.

const str = 
'i need this {client.car.model} exactly at {client.order.time} today';
const data = {
  client: {
    car: {
      model: 'Truck'
    },
    order: {
      time: '12:00PM'
    }
  }
};

const getValueFromPath = (obj, path, delimiter = '.') => {
  // path or obj are falsy, just return obj
  // you could tweak this bit to do something else if you want
  // obj === undefined might be from our recursive call, so keep that in mind if you tweak
  if (!path || !obj) return obj;

  const parts = path.split(delimiter);
  const next = parts.shift(); // get the first part, parts now has all the other parts
  
  // If !parts.length (parts.length === 0), we're on the last part, so we'll return.
  if (!parts.length) return obj[next];
  
  // Otherwise, recurse with the rest of the parts.
  return getValueFromPath(obj[next], parts.join(delimiter), delimiter);
};

const result = str.replace(/{(.+?)}/gi, (_, path) => getValueFromPath(data, path));
console.log(result);

Upvotes: 0

Sergei Konovalov
Sergei Konovalov

Reputation: 23

I just don't like my currect solution, but it works...

function objReplace(string, object) {
  const re = /{(.+?)}/gi;
  let res = string;
  let regex = re.exec(string);

  while (regex && regex[1]) {
    const ar = regex[1].split('.');
    let obj = object;
    ar.forEach((key) => {
      obj = obj[key];
    });

    obj = obj || '';
    res = res.replace(regex[0], obj);
    regex = re.exec(string);
  }
  return res.replace(/ +/g, ' ');
}

Upvotes: 1

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