按数组内的对象键过滤

Question

Using the provided example from MDN (in the 'Searching in array' example half way down that page) , how do I change this to be able to filter by by object key on an object inside an array? Right now it's getting the error: TypeError: el.toLowerCase is not a function .

 var searchTerm = "lotty"; var arr = [ {user: "William", message:"meet me in the nanoscale library"}, {user: "Lotty", message:"sounds like a plan"} ]; function filterItems(query) { return arr.filter(function(el) { return el.toLowerCase().indexOf(query.toLowerCase()) > -1; }) } var filteredArr = filterItems(searchTerm); console.log(filteredArr); 

Answer 1

el is the object being iterated over, not the user string, so el.toLowerCase() doesn't work. For what you want, destructure the el into the user first:

 var newUser = "lotty"; var arr = [ {user: "William", message:"meet me in the nanoscale library"}, {user: "Lotty", message:"sounds like a plan"} ]; function filterItems(query) { return arr.filter(function({ user }) { return user.toLowerCase().indexOf(query.toLowerCase()) > -1; }) } var filteredArr = filterItems(newUser); console.log(filteredArr); 

Or, more tersely, using modern syntax and .includes :

 var newUser = "lotty"; var arr = [ {user: "William", message:"meet me in the nanoscale library"}, {user: "Lotty", message:"sounds like a plan"} ]; const filterItems = query => arr.filter( ({ user }) => user.toLowerCase().includes(query.toLowerCase()) ); var filteredArr = filterItems(newUser); console.log(filteredArr); 

Answer 2

CertainPerformance's answer is verygood. But if u want to use destructure, you must sure the object has user key. like this: user&&user.toLowerCase().includes(query.toLowerCase())