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Getting Data From the Web

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Getting Data From the Web

In this article, we'll look at a way to get/copy a table from a Wikipedia web page, using a simple JavaScript syntax for data scraping.

· Web Dev Zone ·
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Deploying code to production can be filled with uncertainty. Reduce the risks, and deploy earlier and more often. Download this free guide to learn more. Brought to you in partnership with Rollbar.

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In this article, I will show you a nice and clever way to get/copy a table from a Wikipedia web page, using a simple JavaScript syntax. If you are not familiar with JavaScript, don’t worry, you can still follow along.

By the way, this process is often described as scraping data with a browser.

Let’s start!

Go to the following Wikipedia web page. Scroll down to the economy section. Switch to the developer tool:

  • On Internet Explorer: press F12.

  • On Google Chrome: click on the menu, then More Tools, and select the Developer Tools (see picture below).

Now it is time to select the table to copy the data. Click on the arrow of the Developer Tools, then click on the first element of the first table, and click on the <tbody> tag to select the table (see below):

Notice that there is a $0 after the tag <tbody>, this sign allows us to process the element table, in other words, the $0 is the table now.

Click on the Console tab.

Then write $0 and click enter.

The table select earlier is now on the console.

Cool, right!

To save the table write this code and press enter:
var wholeTable = $$("tr", $0)

Warning:
Be sure to use the straight apostrophe instead of the curly apostrophe around the tr.

To access any cell in the table, e.g., the first cell, use this code and press enter:
wholeTable[0].cells[0].innerText

The table is a set of lines and columns, and this is how it is accessible: wholeTable[Line].cells[Column]. The inneText is just a way to display the data in the cell.

Now, let’s get the data by making the following loop:

var tempObj = [];
for (i = 0; i < wholeTable.length; i++) {
    tempObj[i] = {
        Country: "",
        GDP: ""
    };

    //Copy the first column
    tempObj[i].Country = wholeTable[i].cells[1].innerText;

    //Copy the second column
    tempObj[i].GDP = parseFloat(wholeTable[i].cells[2].innerText.replace(/[^\d\.\-]/g, ""));
}

I create an empty object tempObj (an array) to copy the cells’ data in the object properties’ Country and GDP.

Remark

If you are using another table, feel free to write the titles that correspond to the table you would like to copy.

You can copy any column by adding this line of code with the right column number: wholeTable[i].cells[NumberOfTheColumn].innerText; 

The following line parseFloat(wholeTable[i].cells[2].innerText.replace(/[^\d\.\-]/g, “”) is just a trick to convert the text to a value, otherwise I will get a string instead of a value.

Well, guess what, the table is ready. The last step is to copy and paste the tempObj and use it in any environment you want. Write copy(tempObj) and press enter. Check here.

Feel free to share your experience using this method or another method. You are also welcome to ask any questions about this topic.

Have a nice day!

Deploying code to production can be filled with uncertainty. Reduce the risks, and deploy earlier and more often. Download this free guide to learn more. Brought to you in partnership with Rollbar.

Topics:
javascript ,web scraping ,web dev ,data scraping

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