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JavaScript Answers

How to load totally new data with Chart.js and JavaScript?

Sometimes, we want to load totally new data with Chart.js and JavaScript.

In this article, we’ll look at how to load totally new data with Chart.js and JavaScript.

How to load totally new data with Chart.js and JavaScript?

To load totally new data with Chart.js and JavaScript, we call destroy on the existing chart and then we create a new chart.

To do this, we write

myLineChart.destroy();

to destroy the myLineChart chart with destroy.

Then we write

const ctx = document.getElementById("myChartLine").getContext("2d");
myLineChart = new Chart(ctx).Line(data, options);

to get the canvas with getElementById.

Then we get the canvas context with getContext.

Finally, we create the new chart with the Chart constructor and the Line method.

Conclusion

To load totally new data with Chart.js and JavaScript, we call destroy on the existing chart and then we create a new chart.

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JavaScript Answers

How to add a variable to console.log with JavaScript?

Sometimes, we want to add a variable to console.log with JavaScript.

In this article, we’ll look at how to add a variable to console.log with JavaScript.

How to add a variable to console.log with JavaScript?

To add a variable to console.log with JavaScript, we can pass it in as an argument.

For instance, we write

console.log("story", name, "story");

to log the value of name as the 2nd entry in the console log between the 2 'story' strings.

Conclusion

To add a variable to console.log with JavaScript, we can pass it in as an argument.

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JavaScript Answers

How to create a custom InfoWindow with Google Maps and JavaScript?

Sometimes, we want to create a custom InfoWindow with Google Maps and JavaScript.

In this article, we’ll look at how to create a custom InfoWindow with Google Maps and JavaScript.

How to create a custom InfoWindow with Google Maps and JavaScript?

To create a custom InfoWindow with Google Maps and JavaScript, we use the InfoWindow constructor.

For instance, we write

const infowindow = new google.maps.InfoWindow();

google.maps.event.addListener(
  marker,
  "mouseover",
  ((marker) => {
    return () => {
      const content = address;
      infowindow.setContent(content);
      infowindow.open(map, marker);
    };
  })(marker)
);

to call the InfoWindow constructor with an object with the content of the InfoWindow.

Then we add a mouseover event listener to the marker.

In the event listener, we have

infowindow.setContent(content)

to set the content of the InfoWindow to the content string.

And then we call open to open the InfoWindow on the marker on the map.

Conclusion

To create a custom InfoWindow with Google Maps and JavaScript, we use the InfoWindow constructor.

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JavaScript Answers

How to convert a string to long in JavaScript?

Sometimes, we want to convert a string to long in JavaScript.

In this article, we’ll look at how to convert a string to long in JavaScript.

How to convert a string to long in JavaScript?

To convert a string to long in JavaScript, we can convert it to a bigint.

For instance, we write

const bi = BigInt("1274836528318476135");

to convert the "1274836528318476135" string to a bigint with the BigInt function.

Conclusion

To convert a string to long in JavaScript, we can convert it to a bigint.

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JavaScript Answers

How to update the Context value in a Provider from the Consumer with React?

Sometimes, we want to update the Context value in a Provider from the Consumer with React.

In this article, we’ll look at how to update the Context value in a Provider from the Consumer with React.

How to update the Context value in a Provider from the Consumer with React?

To update the Context value in a Provider from the Consumer with React, we pass the state setter function from the provider so it can be retrieved by the consumer.

For instance, we create the authContext.js file with

import { createContext } from "react";

const authContext = createContext({
  authenticated: false,
  setAuthenticated: (auth) => {}
});

export default authContext;

We call createContext to create the context with an object with some data we want to share.

Next, in login.js, we write

import React, { useContext } from "react";
import authContext from "./authContext";

export default () => {
  const { setAuthenticated } = useContext(authContext);
  const handleLogin = () => setAuthenticated(true);
  const handleLogout = () => setAuthenticated(false);

  return (
    <React.Fragment>
      <button onClick={handleLogin}>login</button>
      <button onClick={handleLogout}>logout</button>
    </React.Fragment>
  );
};

to call useContext to get the authContext.

And then we call the setAuthenticated function to set the value of authenticated.

Finally, we write

import ReactDOM from "react-dom";
import React, { useState } from "react";

import authContext from "./authContext";
import Login from "./Login";

const App = () => {
  const [authenticated, setAuthenticated] = useState(false);

  return (
    <authContext.Provider value={{ authenticated, setAuthenticated }}>
      <div> user is {`${authenticated ? "" : "not"} authenticated`} </div>
      <Login />
    </authContext.Provider>
  );
};

ReactDOM.render(<App />, document.getElementById("container"));

in index.js to call useState to create the authenticated state.

We pass authenticated and setAuthenticated into the context by setting the value prop of authContext.Provider to an object with authenticated and setAuthenticated.

As a result, we call call it in login.js since we pass the values in the provider.

Conclusion

To update the Context value in a Provider from the Consumer with React, we pass the state setter function from the provider so it can be retrieved by the consumer.

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