How to pass lambda as parameter in Javascript?

Question

I have a big function in Javascript that I need to repeat the same logic, except for the line bellow, that is different:

config.some(x => x.site === text)

The other function will do the same thing, but instead of filtering by SITE, it will filter by NAME:

config.some(x => x.name === text)

I want to pass SITE or NAME as a parameter to the method. How can I do this?

I was hoping for something like this:

myMethod(lambda) {
   config.some(lambda === text)
}

And call like:

this.myMethod(x => x.site);

myMethod(lambda) { return config.some(x => lambda(x) === text); } — ASDFGerte
– ASDFGerte, Commented Nov 7, 2019 at 19:43

Vlad Vidac · Accepted Answer · 2019-11-07 19:55:40Z

9

If you want to pass the parameter name it could be done like this:

myMethod(key) {
   config.some(x => x[key] === text)
}
myMethod('name');

A "lambda" passing implementation would look like:

myMethod(lambda) {
   config.some(x => lambda(x) === text)
}
const nameLambda = (x) => x.name;
myMethod(nameLambda);

edited Nov 7, 2019 at 19:55

answered Nov 7, 2019 at 19:39

Vlad Vidac

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3 Comments

alansiqueira27 Over a year ago

Hi, I'm getting this error: "x is not defined". Can you please review this line? config.some(x[key] === text)

Vlad Vidac Over a year ago

I don't know where your x is, you used it in your example as if it were defined there.

alansiqueira27 Over a year ago

Ah got it! Then I should do this: config.some(x => x[key] === text). Thanks!

Nicolas · Accepted Answer · 2019-11-07 19:40:14Z

4

You can pass the lambda argument directly to the some function.
Here is an example with filter.

function methodWithLambda(lambda) {
  let data = [
    1,2,3,4,5,6,7,8
  ]
  
  return data.filter(lambda);
}

console.log(methodWithLambda(x => x > 4));
console.log(methodWithLambda(x => x < 7));

answered Nov 7, 2019 at 19:40

Nicolas

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