D3.js | d3.ascending() Function

Last Updated : 23 Aug, 2019
The d3.ascending() function in D3.js is a built-in comparator function for the natural order which accepts two parameters and computes their natural order. Syntax: 
d3.ascending(x, y)
Parameters: This function accepts two parameters x, y whose natural order needs to be computed. Return Value: The function has the following return values:
  • Returns -1 if the two values are in ascending order.
  • Returns 1 if the two values are in descending order.
  • Returns 0 if the two values are equal
  • Returns NaN if there are no comparable values, i.e. only one or no parameters are passed to the function.
Below programs illustrate the d3.ascending() function in D3.js. Example 1: html 
<!DOCTYPE html>
<html>

<head>
    <title>D3.js | d3.ascending() function</title>

    <script src='https://d3js.org/d3.v4.min.js'></script>
</head>

<body>
    <script>
        // If the two values are in 
        // ascending order
        document.write(d3.ascending(33, 64) + "<br>"); // -1

        // If the two values are in 
        // descending order
        document.write(d3.ascending(42, 24) + "<br>"); // 1

        // If the two values are equal
        document.write(d3.ascending(43, 43) + "<br>"); // 0
    </script>
</body>

</html>
Output: 
-1
1
0
Example 2: html 
<!DOCTYPE html>
<html>

<head>
    <title>D3.js d3.ascending() function</title>

    <script src='https://d3js.org/d3.v4.min.js'></script>
</head>

<body>
    <script>
        // If no values are passed
        document.write(d3.ascending() + "<br>"); // NaN

        // If only one value is passed
        document.write(d3.ascending(42) + "<br>"); // NaN

        // If the two values are equal
        document.write(d3.ascending("x", "x") + "<br>"); // 0

        // If the two values are in
        // ascending order
        document.write(d3.ascending("x", "y") + "<br>"); // -1

        // If the two values are in
        // descending order
        document.write(d3.ascending("y", "x") + "<br>"); // 1
    </script>
</body>

</html>
Output: 
NaN
NaN
0
-1
1
Reference:https://devdocs.io/d3~5/d3-array#ascending
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