How does uniapp realize the longitude and latitude distance between two places?

In modern society, as the pace of people's lives becomes faster, more and more people need to work or travel across different cities or countries, and understanding the distance between two places has become a basic need. In this case, calculating the distance between every two locations becomes increasingly important. However, calculating these distances in real situations is a relatively complex task. Fortunately, now we have the uniapp framework to help us.

uniapp is an efficient and fast front-end cross-platform development framework. It is based on Vue.js and can support rapid development on multiple platforms. In uniapp, we can use its API to quickly calculate the distance between two locations to help implement this function.

First, we need an API that can calculate the distance between two locations using latitude and longitude. We can use Haversine's formula, which is a formula used to calculate the distance between two points on the spherical surface of the earth. The Haversine formula takes the longitude and latitude of two points as input and then outputs the distance between them in kilometers. Since there is no native haversine function in JavaScript, we need to implement it manually.

Next, we need to get the user’s location coordinates. We can use the API uni.getLocation() provided by uniapp to obtain the user's current location information. This API returns a JS object containing user location information, including longitude and latitude. We can store this location information in variables for later use.

Once we have the user's location information, we can add another location information to the application. We can ask the user to enter latitude and longitude information for another location, or get it from a database or server. For the example here, let's manually enter the latitude and longitude information for another location, stored in another variable.

Through the above steps, we have obtained the latitude and longitude information of the two locations. Now we can pass this information to the Haversine formula we just implemented to get the distance between two locations. The function that implements Haversine's formula looks like this:

function getDistanceFromLatLonInKm(lat1,lon1,lat2,lon2) {
    const R = 6371; // 地球半径（千米）
    const dLat = deg2rad(lat2-lat1); // deg2rad函数用于将角度转换为弧度
    const dLon = deg2rad(lon2-lon1); 
    const a = 
    Math.sin(dLat/2) * Math.sin(dLat/2) +
    Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * 
    Math.sin(dLon/2) * Math.sin(dLon/2); 
    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
    const distance = R * c; // 单位：千米
    return distance;
}

In the above function, we take as input the latitude and longitude of two locations and calculate the distance between them using the standard formula. By calling this function we can calculate the distance between two locations.

Finally, we can display the calculated distance in the application to display to the user. This can be done with simple HTML and CSS.

To summarize, uniapp is a very powerful front-end framework. It provides a rich API and components that can help developers easily implement various functions. In this article, we explored how to use uniapp to calculate the distance between two locations. We implemented our own distance calculation function using the Haversine formula, and obtained the user's location information using uniapp's API uni.getLocation(). Finally, we display the calculated distance on the page.

In actual development, we can apply this function to various different scenarios. For example, in a travel application we can use this feature to calculate the distance to different destinations. Alternatively, in a logistics management application, we can use this function to calculate the transportation distance of goods between different locations.

All in all, we believe this feature will be of great help to many developers, allowing them to work from a more efficient perspective and provide a better experience for their users.

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