Category: JavaScript

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JavaScript Answers

How to pass object by value with JavaScript?

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Sometimes, we want to pass object by value with JavaScript.

In this article, we’ll look at how to pass object by value with JavaScript.

How to pass object by value with JavaScript?

To pass object by value with JavaScript, we make a copy of the object.

For instance, we write

const obj2 = { ...obj1 };
foo(obj2);

to make a shallow copy of obj1 with the spread operator and assign the copied object to obj2.

Then we call foo with obj2 without affecting obj1.

Conclusion

To pass object by value with JavaScript, we make a copy of the object.

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JavaScript Answers

How to initialize an array with a single value with JavaScript?

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Sometimes, we want to initialize an array with a single value with JavaScript.

In this article, we’ll look at how to initialize an array with a single value with JavaScript.

How to initialize an array with a single value with JavaScript?

To initialize an array with a single value with JavaScript, we can create an empty array and then call map to map each entry to the value we want.

For instance, we write

const arr = [...new Array(1000000)].map(() => 42);

to create array arr with length 1000000.

And then we call map with a callback that maps each entry to 42.

Then arr has 1000000 42’s in it.

Conclusion

To initialize an array with a single value with JavaScript, we can create an empty array and then call map to map each entry to the value we want.

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Vue Answers

How to listen to the window scroll event in a Vue.js component?

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Sometimes, we want to listen to the window scroll event in a Vue.js component.

In this article, we’ll look at how to listen to the window scroll event in a Vue.js component.

How to listen to the window scroll event in a Vue.js component?

To listen to the window scroll event in a Vue.js component, we can call window.addEventListener.

For instance, we write

export default {
  created() {
    window.addEventListener("scroll", this.handleScroll);
  },
  destroyed() {
    window.removeEventListener("scroll", this.handleScroll);
  },
  methods: {
    handleScroll(event) {
      // ...
    },
  },
};

to call window.addEventListener in the created hook to add the handleScroll method as the callback for the scroll event when the component is loading.

In the destroyed hook, we call window.removeEventListener to remove handleScroll as the scroll event listener when the component unmounts.

Conclusion

To listen to the window scroll event in a Vue.js component, we can call window.addEventListener.

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JavaScript Answers

How to remove all multiple spaces in JavaScript and replace with single space?

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Sometimes, we want to remove all multiple spaces in JavaScript and replace with single space.

In this article, we’ll look at how to remove all multiple spaces in JavaScript and replace with single space.

How to remove all multiple spaces in JavaScript and replace with single space?

To remove all multiple spaces in JavaScript and replace with single space, we use the string replace method with a regex.

For instance, we write

str = str.replace(/ +(?= )/g, "");

to call str.replace with the / +(?= )/g regex to match all instances of multiple spaces in the str string.

We use +(?= ) to match multiple spaces.

And we use the g flag to find all matches.

Then we replace them all with empty strings.

Conclusion

To remove all multiple spaces in JavaScript and replace with single space, we use the string replace method with a regex.

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JavaScript Answers

How to find the longest string in an array with JavaScript?

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Sometimes, we want to find the longest string in an array with JavaScript.

In this article, we’ll look at how to find the longest string in an array with JavaScript.

How to find the longest string in an array with JavaScript?

To find the longest string in an array with JavaScript, we can use the array map and Math.max methods.

For instance, we write

const longest = Math.max(...arr.map((el) => el.length));
'``

to call `arr.map` with a callback that returns the `length` of each string `el` and return the lengths in an array.

Then we call `Math.max` with the array entries spread into it as arguments.

This will then return the length of the longest string in `arr`.

### Conclusion

To find the longest string in an array with JavaScript, we can use the array `map` and `Math.max` methods.