How to replace values in array using lodash when flag is true

Question

I have JavaScript object:

myData = {
      items: [
        {
          flag: false,
          text: "good text"
        },
        {
          flag: true,
          text: "good text"
        },
        {
          flag: false,
          text: "good text"
        }
      ]
    }

How can I change text everywhere where flag = true.

For example only 2nd object need to be changed from "good text" to "bad text", because only this object in my example has flag = true.

I want to do this using Lodash in JavaScript.

lagerone · Accepted Answer · 2017-05-26 12:19:48Z

1

If you have to use lodash, this should work:

_.forEach(myData.items, function (item) {
  if (item.flag) {
    item.text = 'bad text';
  }
});

answered May 26, 2017 at 12:19

lagerone

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Comments

Tejasva Dhyani · Accepted Answer · 2017-05-26 12:23:09Z

1

You can use this snippet to change the text.

myData.items = _.map(_.get(myData, 'items'), (item) => {
  if (item.flag) {
    item.text = "new text"
  }
  return item;
});

edited May 26, 2017 at 12:23

answered May 26, 2017 at 12:19

Tejasva Dhyani

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1 Comment

Nico Van Belle Over a year ago

This will not work because item.flag datatype is number and you compare it to a string value.

Fredrik Lundin Grande · Accepted Answer · 2017-05-26 12:21:40Z

0

You really don't need lodash for this..

Here is a solution without using it

myData.items.forEach(item => item.text = item.flag ? "bad text" : item.text)

const myData = {
      items: [
        {
          flag: false,
          text: "good text"
        },
        {
          flag: true,
          text: "good text"
        },
        {
          flag: false,
          text: "good text"
        }
      ]
    };

console.log(JSON.stringify(myData.items));

myData.items.forEach(item => item.text = item.flag ? "bad text" : item.text);

console.log(JSON.stringify(myData.items));

answered May 26, 2017 at 12:21

Fredrik Lundin Grande

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Comments

aquinas · Accepted Answer · 2017-05-26 12:26:45Z

0

How about: _(myData.items).filter('flag').each(x => x.text='bad text');

answered May 26, 2017 at 12:26

aquinas

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4 Comments

Fredrik Lundin Grande Over a year ago

It works, but it will loop the list twice (first full list, then filtered list)

aquinas Over a year ago

Hmm...are you sure, doesn't lodash use lazy evaluation when chaining functions (per the docs): lodash.com/docs/4.17.4#chain

aquinas Over a year ago

Interestingly, depending on how many elements have flag set, the lodash version is faster. See: jsfiddle.net/1vxac6ex/1. This is looping over 10 million records and setting flag to true when i%10 == 0. If we ALWAYS set flag, then your version is quite a bit faster. The "issue" with your version is that it's setting the property for every item, even when it doesn't need to. Ultimately, I like your version better. Using lodash doesn't make sense, but that's what the OP wanted. ¯_(ツ)_/¯

Fredrik Lundin Grande Over a year ago

Wow, very interesting!

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