Spreadsheet

--- id: 5d7925341747ad42b12f8e68 title: Step 42 challengeType: 0 dashedName: step-42 --- # --description-- This is still valid because we're modifying `arr` in place instead of reassigning to it (which is invalid with the `const` keyword). But doing this still modifies state, and we don't want to do that in functional programming. The `concat` method returns a new array instead of modifying an existing one: ```js [1,2,3].concat(4); // [1, 2, 3, 4] [1,2,3].concat(4, 5); // [1, 2, 3, 4, 5] ``` Use `concat` instead of `push` to return the result of adding `end` to `arr`. # --hints-- See description above for instructions. ```js assert( JSON.stringify(range(1, 2)) === '[1,2]' && code.includes('concat') && !code.includes('push') ); ``` # --seed-- ## --before-user-code-- ```html Spreadsheet

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