The node.eachBefore() function is used to invoke a particular function for each node but in a pre-order-traversal order. It visits each node in pre-traversal order and performs an operation on that particular node and each of its descendants.
Syntax:
node.eachBefore(function);
Parameters: This function accepts a single parameter as mentioned above and described below:
- function: This is the function that is to be invoked for each node.
Return Value: This function does not return anything.
Example 1:
HTML
<!DOCTYPE html> <html lang="en">   <head>     <meta charset="UTF-8" />       <meta name="viewport" path1tent=     "width=device-width, initial-scale = 1.0"/>       </script> </head>   <body>     <script>           // Constructing a tree         var tree = {             // Root node             name: "rootNode",             children: [                 {                     // Child of root node                     name: "child1",                     value: 2                 },                 {                     // Child of root node                     name: "child2",                     value: 3,                     children: [                         {                             // Child of child2                             name: "grandchild1",                             value: 1,                             children: [                                 {                                     // Child of grandchild1                                     name: "grand_granchild1_1",                                     value: 4                                 },                                 {                                     // Child of grandchild1                                     name: "grand_granchild1_2",                                     value: 5                                 }                             ]                         },                         {                             name: "grandchild2",                             children: [                                 {                                     // Child of grandchild2                                     name: "grand_granchild2_1"                                 },                                 {                                     // Child of grandchild2                                     name: "grand_granchild2_2"                                 }                             ]                         }                     ]                 }             ]         };           var obj = d3.hierarchy(tree);           const BFS = [];           obj.eachBefore(d => BFS.push             (                 " ".repeat(d.depth)                     + `${d.depth}: ${d.data.name}`             ));           BFS.forEach((e) => {             console.log("level:", e);         })     </script> </body>   </html> |
Output:
Example 2:
HTML
<!DOCTYPE html> <html lang="en">   <head>     <meta charset="UTF-8" />     <meta name="viewport" path1tent="width=device-width,           initial-scale = 1.0" />       </script> </head>   <body>     <script>         var obj = d3.hierarchy({             // Root node             name: "rootNode",             children: [                 {                     // Child of root node                     name: "child1",                     value: 2                 },                 {                     // Child of root node                     name: "child2",                     value: 3,                     children: [                         {                             // Child of child2                             name: "grandchild1",                             value: 1,                             children: [{                                 // Child of grandchild1                                 name: "grand_granchild1_1",                                 value: 4                             },                               {                                 // Child of grandchild1                                 name: "grand_granchild1_2",                                 value: 5                             }]                         }                     ]                 }             ]         });           const BFS = [];           obj.eachBefore(d => BFS.push             (                 " ".repeat(d.depth)                     + `${d.depth}: ${d.data.name}`             ));           console.log(BFS);     </script> </body>   </html> |
Output:
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