Category: JavaScript

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JavaScript Answers

How to generate a 5-digit number in every case with JavaScript?

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Sometimes, we want to generate a 5-digit number in every case with JavaScript.

In this article, we’ll look at how to generate a 5-digit number in every case with JavaScript.

How to generate a 5-digit number in every case with JavaScript?

To generate a 5-digit number in every case with JavaScript, we can use the Math.random method.

For instance, we write

const min = 10000;
const max = 99999;
const num = Math.floor(Math.random() * (max - min + 1)) + min;

to call use Math.random() * (max - min + 1) to generate numbers between 0 and 89999.

And then we add min to that so that num is always a 5 digit number.

Conclusion

To generate a 5-digit number in every case with JavaScript, we can use the Math.random method.

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JavaScript Answers

How to add dynamic key-value pairs to a JavaScript array or hash table?

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Sometimes, we want to add dynamic key-value pairs to a JavaScript array or hash table.

In this article, we’ll look at how to add dynamic key-value pairs to a JavaScript array or hash table.

How to add dynamic key-value pairs to a JavaScript array or hash table?

To add dynamic key-value pairs to a JavaScript array or hash table, we can use computed key names.

For instance, we write

const obj = {};
obj[name] = val;

to add a property with the value of name string as the property name.

We assign val to as the property’s value.

Conclusion

To add dynamic key-value pairs to a JavaScript array or hash table, we can use computed key names.

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JavaScript Answers

How to convert a double to an int in JavaScript without rounding?

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Sometimes, we want to convert a double to an int in JavaScript without rounding.

In this article, we’ll look at how to convert a double to an int in JavaScript without rounding.

How to convert a double to an int in JavaScript without rounding?

To convert a double to an int in JavaScript without rounding, we can use the parseInt function.

For instance, we write

const num = 2.9;
console.log(parseInt(num, 10));

to call parseInt with num and radix 10 to return an integer part of num as the value.

As a result, we see 2 logged from the console log.

Conclusion

To convert a double to an int in JavaScript without rounding, we can use the parseInt function.

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React Answers

How to trigger onChange if input value is changing by state with React?

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Sometimes, we want to trigger onChange if input value is changing by state with React.

In this article, we’ll look at how to trigger onChange if input value is changing by state with React.

How to trigger onChange if input value is changing by state with React?

To trigger onChange if input value is changing by state with React, we can watch for state change with the useEffect hook.

For instance, we write

const MyInputComponent = () => {
  const [numberValue, setNumberValue] = useState(0);
  const numberInput = useRef(null);

  useEffect(() => {
    numberInput.current.dispatchEvent(
      new Event("change", {
        detail: {
          newValue: numberValue,
        },
        bubbles: true,
        cancelable: true,
      })
    );
  }, [numberValue]);

  return (
    <>
      <input
        type="number"
        value={numberValue}
        ref={numberInput}
        inputMode="numeric"
        onChange={(e) => setNumberValue(e.target.value)}
      />
    </>
  );
};

to add an input that’s bound to the numberValue state with the onChange and value props.

value is set to numberValue to display numberValue as the input value.

onChange is set to (e) => setNumberValue(e.target.value) to set the numberValue state to a value.

Then we call useEffect hook with [numberValue] to call the useEffect callback when the numberValue state changes.

Conclusion

To trigger onChange if input value is changing by state with React, we can watch for state change with the useEffect hook.

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JavaScript Answers

How to set the content-type of request header when using Fetch API with JavaScript?

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Sometimes, we want to set the content-type of request header when using Fetch API with JavaScript.

In this article, we’ll look at how to set the content-type of request header when using Fetch API with JavaScript.

How to set the content-type of request header when using Fetch API with JavaScript?

To set the content-type of request header when using Fetch API with JavaScript, we can put the header in a Header object.

For instance, we write

const options = {
  method,
  headers: new Headers({ "content-type": "application/json" }),
  mode: "no-cors",
  body: JSON.stringify(body),
};
await fetch(url, options);

to call fetch to make a request to the url with the request method.

We set headers to a Headers object with the content-type header set to 'application/json'.

body is the stringified request body JSON.

Conclusion

To set the content-type of request header when using Fetch API with JavaScript, we can put the header in a Header object.