javascript - Filter array with multiple startsWith and endsWith arguments - Stack Overflow

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Browsed several different questions/answers surrounding this question, but most rely on includes or indexOf

Problem: How any array to filter (names in this case). I need to filter it using 2 different arrays, one of which has startsWith criteria and the other has endsWith criteria

var names = ['BOB','CATHY','JAKOB','AARON','JUSTICE','BARBARA','DANIEL','BOBBY','JUSTINE','CADEN','URI','JAYDEN','JULIE']
startPatterns = ['BO','JU']
endPatterns = ['EN','ICE']

//res = ['BOB','JUSTICE','JUSTINE','JULIE','JAYDEN','JUSTICE']

Obviously you cannot do names.filter(d => d.startsWith(startPatterns)) because startPatterns is not a string but a array. Something like this isn't working and is terrible slow too:

res=[]
names.forEach(d => {
  endPatterns.forEach(y => d.endsWith(y) ? res.push(d) : '')
  startPatterns.forEach(s => d.startsWith(s) ? res.push(d) : '')})
console.log(res)

Browsed several different questions/answers surrounding this question, but most rely on includes or indexOf

Problem: How any array to filter (names in this case). I need to filter it using 2 different arrays, one of which has startsWith criteria and the other has endsWith criteria

var names = ['BOB','CATHY','JAKOB','AARON','JUSTICE','BARBARA','DANIEL','BOBBY','JUSTINE','CADEN','URI','JAYDEN','JULIE']
startPatterns = ['BO','JU']
endPatterns = ['EN','ICE']

//res = ['BOB','JUSTICE','JUSTINE','JULIE','JAYDEN','JUSTICE']

Obviously you cannot do names.filter(d => d.startsWith(startPatterns)) because startPatterns is not a string but a array. Something like this isn't working and is terrible slow too:

res=[]
names.forEach(d => {
  endPatterns.forEach(y => d.endsWith(y) ? res.push(d) : '')
  startPatterns.forEach(s => d.startsWith(s) ? res.push(d) : '')})
console.log(res)

• javascript

Share Follow asked Dec 13, 2019 at 20:06 K.J.J.KK.J.J.K 43966 silver badges1414 bronze badges 2

• Your code works, it just has problems with duplicates. An easier way is to names.filter(name => startPatterns.some(p => name.startsWith(p)) || endPatterns.some(p => name.endsWith(p))); – ASDFGerte Commented Dec 13, 2019 at 20:11
• 2 forEach does not return anything, so the usage of an expression bodied function and there a misappropriation of ?: to push – crashmstr Commented Dec 13, 2019 at 20:11

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 7

You can use Array.prototype.some on the pattern arrays to achieve this:

let filtered = names.filter(name => (
  startPatterns.some(pattern => name.startsWith(pattern)) ||
  endPatterns.some(pattern => name.endsWith(pattern))
))

The logic here being "Return true if the name begins with at least one of the start patterns OR ends with at least one of the end patterns".

You could build a regular expression and check the string against the pattern.

var names = ['BOB','CATHY','JAKOB','AARON','JUSTICE','BARBARA','DANIEL','BOBBY','JUSTINE','CADEN','URI','JAYDEN','JULIE'],
    startPatterns = ['BO','JU'],
    endPatterns = ['EN','ICE'],
    regexp = new RegExp(`^(${startPatterns.join('|')})|(${endPatterns.join('|')})$`),
    result = names.filter(s => regexp.test(s));

console.log(result);

A non regular expression approach with an array with the methods and wanted values.

var names = ['BOB','CATHY','JAKOB','AARON','JUSTICE','BARBARA','DANIEL','BOBBY','JUSTINE','CADEN','URI','JAYDEN','JULIE'],
    patterns = [['startsWith', ['BO','JU']], ['endsWith', ['EN','ICE']]],
    result = names.filter(s => patterns.some(([k, values]) => values.some(v => s[k](v))));

console.log(result);

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