Getting values from array that matches a regular expression using lodash

Question

My json array:

[{"id":"7","name":"hello"},{"id":"7","name":"shan"},{"id":"7","name":"john"}
{"id":"7","name":"hello"}]

I want to get a new array that matches a regular expression on name starting with a letter.

I am using regexp but i don't know how to implement it.

Here is my code:

var newitem=_.filter(result,item=>item.name='hello');
 console.log(newitem);

But it returns with only strict match of name.

Please help me to modify the above so that the result is a new array as described.

Expected output

when a usertype letter h it shows only the row

{"id":"7","name":"hello"}

Note that `item.name='hello'` will assign the string value. You need to use `==` or `===`. — Tushar, Feb 19 '16 at 05:09
Shouldn't expected output contain two objects as there are two objects whose `name` starts with `h`. — Tushar, Feb 19 '16 at 05:32

Tushar · Accepted Answer · 2016-02-19T05:29:09.653

14

To check if the name starts with a string, you can use RegExp#test with regex.

var newItem = _.filter(result, obj => /^[a-zA-Z]/.test(obj.name));

The regex ^[a-zA-Z] will check if the name starts with alphabet.

var arr = [{
    "id": "7",
    "name": "hello"
}, {
    "id": "7",
    "name": "shan"
}, {
    "id": "7",
    "name": "jhon"
}, {
    "id": "7",
    "name": "hello"
}, {
    id: 10,
    name: '$haun'
}];

var newItem = _.filter(arr, obj => /^[a-zA-Z]/.test(obj.name));
console.log(newItem);

<script src="https://cdnjs.com/libraries/lodash.js/"></script>

Same code can be written using Array#filter.

arr.filter(obj => /^[a-zA-Z]/.test(obj.name));

var arr = [{
    "id": "7",
    "name": "hello"
}, {
    "id": "7",
    "name": "*shan"
}, {
    "id": "7",
    "name": "jhon"
}, {
    "id": "7",
    "name": "hello"
}, {
    id: 10,
    name: '$haun'
}];

var newItem = arr.filter(obj => /^[a-zA-Z]/.test(obj.name));
console.log(newItem);
document.body.innerHTML = '<pre>' + JSON.stringify(newItem, 0, 4) + '</pre>';

Update:

when a usertype letter h it shows only the row

You can use

_.filter(result, obj => /^h/.test(obj.name));

Use i-case insensitive flag to match the alphabet irrespective of the case. That'll match both h and H.

edited Feb 19 '16 at 05:29

answered Feb 19 '16 at 05:02

Tushar

85,780
21
159
179

But it will returns all the rows – Blessan Kurien Feb 19 '16 at 05:15
@BlessanKurien You said _I want to get a new array that matches a regular expression on name starting with a letter._ right. What is expected output? – Tushar Feb 19 '16 at 05:18
@BlessanKurien Do you want to filter the objects whose name starts with `h`, then you just need to use `/^h/` regex. Use `i` flag to match case-insensitively i.e. both `h` and `H`. – Tushar Feb 19 '16 at 05:20
Updated my question with expected output – Blessan Kurien Feb 19 '16 at 05:26
I am asking regular expression in lodash library https://lodash.com/docs#isRegExp – Blessan Kurien Feb 19 '16 at 05:27
@BlessanKurien Check update at the bottom of the answer. And the expected output should `[{"id":"7","name":"hello"}, {"id":"7","name":"hello"}]` as their `name` starts with `h`. – Tushar Feb 19 '16 at 05:30
@BlessanKurien You don't need `isRegExp`, it _Checks if value is classified as a RegExp object._. You don't want to check if the value of `name` is regex. – Tushar Feb 19 '16 at 05:31
ok one more question instead of letter `h` i want to place variable – Blessan Kurien Feb 19 '16 at 05:33
@BlessanKurien You need `RegExp` constructor. Check [How do you pass a variable to a Regular Expression JavaScript?](http://stackoverflow.com/questions/494035/how-do-you-pass-a-variable-to-a-regular-expression-javascript) – Tushar Feb 19 '16 at 05:34
bcz when user type a keyword it is assigned to a variable and returns the rows based on that match – Blessan Kurien Feb 19 '16 at 05:34
I am using this way `'/^'+keyword+'/'.test(item.name)` but it gives an error `"/".test is not a function` – Blessan Kurien Feb 19 '16 at 05:37
@BlessanKurien Use `new RegExp("^" + keyword).test(...` – Tushar Feb 19 '16 at 05:42
@BlessanKurien No, you didn't mention that the keyword is dynamic. – Tushar Feb 19 '16 at 05:43
I've tried this `new RegExp("/^"+keyword+"/").test(item.name)` but returns null result – Blessan Kurien Feb 19 '16 at 05:45
@BlessanKurien READ MY LAST [COMMENT](http://stackoverflow.com/questions/35497598/getting-values-from-array-that-matches-a-regular-expression-using-loadash#comment58688101_35497671). YOU DON"T NEED `/`. – Tushar Feb 19 '16 at 05:45

score 0 · Answer 2 · answered Feb 19 '16 at 06:09

0

regex ('^h.') should work on this. To get row with name h.

answered Feb 19 '16 at 06:09

Rajesh Mappu

483
9
23

Getting values from array that matches a regular expression using lodash

2 Answers2