nest.map() function in D3.js is used to form a nested map. The map contains a key-value pair determined by the key function which was executed very first. If no keys are declared or defined than map function returns the original array as it is.
Syntax:
nest.map(array)
- It takes the collection array as the input.
Parameters:
Return:
Below are a few examples of the above function
Example 1:
When keys are defined.
<!DOCTYPE html> <html lang="en"> <head>   <meta charset="UTF-8">   <meta name="viewport"         content="width=device-width,                  initial-scale=1.0">   <title>Document</title> </head> <style>   .originalColor{     height: 100px;     width: 100px;   }   .darkerColor{     height: 100px;     width: 100px;   } </style> <body>       <!-- Fetching from CDN of D3.js -->  <script type = "text/javascript"           src =    </script>   <script>     // Forming the collection     let coll=[       {val:"val10", data:"data11"},       {val:"val20", data:"data22"},       {val:"val30", data:"data33"},       {val:"val40", data:"data44"}     ]     let data= d3.nest()                 .key(function(d) {       return d.val; })                 .map(coll)     // Logging the data     console.log(data);   </script> </body> </html> |
Output:
Example 2:
When no keys are defined.
<!DOCTYPE html> <html lang="en"> <head>   <meta charset="UTF-8">   <meta name="viewport"         content="width=device-width,                  initial-scale=1.0">   <title>Document</title> </head> <style>   .originalColor{     height: 100px;     width: 100px;   }   .darkerColor{     height: 100px;     width: 100px;   } </style> <body>       <!--fetching from CDN of D3.js -->  <script type = "text/javascript"   </script>   <script>     let collection=[       {val:"val10", data:"data11"},       {val:"val20", data:"data22"},     ]     //no keys are defined     let data= d3.nest()                 .map(collection)     console.log(data);   </script> </body> </html> |
Output:
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