31:T7ac,md ` [#](https://github.com/d3/d3-selection/blob/master/README.md#selection_merge) *selection*.**merge**(*other*) [<>](https://github.com/d3/d3-selection/blob/master/src/selection/merge.js) Returns a new selection merging this selection with the specified *other* selection. The returned selection has the same number of groups and the same parents as this selection. Any missing (null) elements in this selection are filled with the corresponding element, if present (not null), from the specified *selection*. (If the *other* selection has additional groups or parents, they are ignored.) This method is used internally by [*selection*.join](https://github.com/d3/d3-selection/blob/master/README.md#selection_join) to merge the [enter](https://github.com/d3/d3-selection/blob/master/README.md#selection_enter) and [update](https://github.com/d3/d3-selection/blob/master/README.md#selection_data) selections after [binding data](https://github.com/d3/d3-selection/blob/master/README.md#joining-data). You can also merge explicitly, although note that since merging is based on element index, you should use operations that preserve index, such as [*selection*.select](https://github.com/d3/d3-selection/blob/master/README.md#selection_select) instead of [*selection*.filter](https://github.com/d3/d3-selection/blob/master/README.md#selection_filter). For example: \`\`\`js const odd = selection.select(function(d, i) { return i & 1 ? this : null; )); const even = selection.select(function(d, i) { return i & 1 ? null : this; )); const merged = odd.merge(even); \`\`\` See [*selection*.data](https://github.com/d3/d3-selection/blob/master/README.md#selection_data) for more. This method is not intended for concatenating arbitrary selections, however: if both this selection and the specified *other* selection have (non-null) elements at the same index, this selection’s element is returned in the merge and the *other* selection’s element is ignored. `32:[] 2f:{"title":"d3.selection.merge","cells":[{"id":0,"value":"md`# d3.selection.merge`","pinned":false,"hidden":false,"mode":"ojs"},{"id":10,"value":"{\n const c = html`\n

\n`\n const odd = d3.select(c).selectAll(\"p\").select(function(d, i) { return i & 1 ? this : null; });\n // const even = selection.select(function(d, i) { return i & 1 ? null : this; ));\n // const merged = odd.merge(even);\n return odd \n\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":15,"value":"{\n const c = html`\n

\n`\n // const odd = d3.select(c).selectAll(\"p\").select(function(d, i) { return i & 1 ? this : null; });\n const even = d3.select(c).selectAll(\"p\").select(function(d, i) { return i & 1 ? null : this; });\n // const merged = odd.merge(even);\n return even \n\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":17,"value":"{\n const c = html`\n

\n`\n const odd = d3.select(c).selectAll(\"p\").select(function(d, i) { return i & 1 ? this : null; });\n const even = d3.select(c).selectAll(\"p\").select(function(d, i) { return i & 1 ? null : this; });\n const merged = odd.merge(even);\n return merged \n\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":5,"value":"$31","pinned":false,"hidden":false,"mode":"ojs"},{"id":8,"value":"import { d3 } from \"@embracelife/tutorial-utilities\"","pinned":true,"hidden":false,"mode":"ojs"}],"files":"$W32","stdlib":"1","titling":"auto"}