How to use TypeScript to filter arrays with multiple dimensions

I've been attempting to filter an array with multiple filters, but I can't seem to achieve the desired outcome so far.

This is my Angular component:

list = [ {type: type1, code: code1}, {type: type2, code: code2}]

searchElement(code?: string, type?: string){
var myVar = this.list

if(type)
myVar = myVar.filter(elt => elt.type.indexOf(type) > -1);

if(code)
myVar = myVar.filter(elt => elt.type.indexOf(code) > -1);

//call another function myFunction() with the filtered array myVar
}

Due to its asynchronous behavior, myFunction() is being called before myVar is properly filtered. How can I ensure that myVar is fully filtered before calling myFunction()?

javascriptangulartypescript

Answer №1

To efficiently filter values, it is recommended to combine both filter conditions into a single filter callback function instead of using multiple filter calls:

list = [ {type: type1, code: code1}, {type: type2, code: code2}];

searchElement(code?: string, type?: string){
    var myVar = this.list;

    if (type || code) {
        myVar = myVar.filter(elt => (!type || elt.type.indexOf(type) > -1) && (!code || elt.code.indexOf(code) > -1));
    }

    // ...
}

Each condition follows the pattern 

!filterValue || useTheFilterValue
, ensuring that if there is no filter value, the condition is met, and if there is, it only applies if the filter matches.

This implementation assumes an "and" match requirement, hence why the two filtering checks are joined with &&. For instance, when providing both type and code, both must match for an element to be retained in the array.

(Additionally, there was a mistake where code was being compared against elt.type instead of elt.code.)

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