In javascript, how can I check if a string starts with any of the strings in an array.
For example,
I have an array of strings,
const substrs = ['the', 'an', 'I']; I have a string
const str = 'the car'; How can I check if str starts with any of the strings in substrs?
You can use a combination of Array.prototype.some and String.prototype.startsWith, both of which are ES6 features:
const substrs = ['the', 'an', 'I']; function checkIfStringStartsWith(str, substrs) { return substrs.some(substr => str.startsWith(substr)); } console.log(checkIfStringStartsWith('the car', substrs)); // true console.log(checkIfStringStartsWith('a car', substrs)); // false console.log(checkIfStringStartsWith('i am a car', substrs)); // false console.log(checkIfStringStartsWith('I am a car', substrs)); // trueIf you want the comparsion to be done in a case-insensitive manner, then you will need to convert the string to lowercase as well:
const substrs = ['the', 'an', 'I']; function checkIfStringStartsWith(str, substrs) { return substrs.some(substr => str.toLowerCase().startsWith(substr.toLowerCase())); } console.log(checkIfStringStartsWith('the car', substrs)); // true console.log(checkIfStringStartsWith('a car', substrs)); // false console.log(checkIfStringStartsWith('i am a car', substrs)); // true (case-insensitive) console.log(checkIfStringStartsWith('I am a car', substrs)); // true
const substrs = ['the', 'an', 'I']; const str = 'the car'; let result = substrs.filter(s => str.startsWith(s)); console.log(result);
str.startsWith(s) here what is str and what is s?
I , the , an. In your case and,Interest,them are also considered.
One approach would be to build a regex alternation of the keywords in the substrs array. Then, use test() on the input to check for a match:
const substrs = ['the', 'an', 'I']; const str = 'the car'; regexp = new RegExp('^(?:' + substrs.join('|') + ')\\b'); console.log(regexp); if (regexp.test(str)) { console.log("MATCH"); }Here I have also printed out the regular expression being used so that it is clear.
., + and *. Then you need to start thinking about escaping things and it becomes an even more overengineered solution.
const check = (arr, str) => { const firstWord = str.substr(0, str.indexOf(" ")); return arr.includes(firstWord); } const substrs = ['thee', 'an', 'I', 'The', 'the']; const str = 'the car'; console.log(check(substrs, str)); //true 
theand likethere was a car? should that match or not?['the', 'an', 'I'].toLocaleString()to getthe,an,Iand you have two strings and can manipulate them