Let's say I have an array with many Strings Called "birdBlue", "birdRed" and some other animals like "pig1", "pig2").
Now I run a for loop that goes through the array and should return all birds. What comparison would make sense here?
Animals == "bird*" was my first idea but doesn't work. Is there a way to use the operator * (or is there something similar to use?
This question is related to
javascript
string
comparison
This function convert wildcard to regexp and make test (it supports . and * wildcharts)
function wildTest(wildcard, str) {
let w = wildcard.replace(/[.+^${}()|[\]\\]/g, '\\$&'); // regexp escape
const re = new RegExp(`^${w.replace(/\*/g,'.*').replace(/\?/g,'.')}$`,'i');
return re.test(str); // remove last 'i' above to have case sensitive
}
function wildTest(wildcard, str) {_x000D_
let w = wildcard.replace(/[.+^${}()|[\]\\]/g, '\\$&'); // regexp escape _x000D_
const re = new RegExp(`^${w.replace(/\*/g,'.*').replace(/\?/g,'.')}$`,'i');_x000D_
return re.test(str); // remove last 'i' above to have case sensitive_x000D_
}_x000D_
_x000D_
_x000D_
// Example usage_x000D_
_x000D_
let arr = ["birdBlue", "birdRed", "pig1z", "pig2z", "elephantBlua" ];_x000D_
_x000D_
let resultA = arr.filter( x => wildTest('biRd*', x) );_x000D_
let resultB = arr.filter( x => wildTest('p?g?z', x) );_x000D_
let resultC = arr.filter( x => wildTest('*Blu?', x) );_x000D_
_x000D_
console.log('biRd*',resultA);_x000D_
console.log('p?g?z',resultB);_x000D_
console.log('*Blu?',resultC);Instead Animals == "bird*" Animals = "bird*" should work.
if(mas[i].indexOf("bird") == 0)
//there is bird
You.can read about indexOf here: http://www.w3schools.com/jsref/jsref_indexof.asp
var searchArray = function(arr, str){
// If there are no items in the array, return an empty array
if(typeof arr === 'undefined' || arr.length === 0) return [];
// If the string is empty return all items in the array
if(typeof str === 'undefined' || str.length === 0) return arr;
// Create a new array to hold the results.
var res = [];
// Check where the start (*) is in the string
var starIndex = str.indexOf('*');
// If the star is the first character...
if(starIndex === 0) {
// Get the string without the star.
str = str.substr(1);
for(var i = 0; i < arr.length; i++) {
// Check if each item contains an indexOf function, if it doesn't it's not a (standard) string.
// It doesn't necessarily mean it IS a string either.
if(!arr[i].indexOf) continue;
// Check if the string is at the end of each item.
if(arr[i].indexOf(str) === arr[i].length - str.length) {
// If it is, add the item to the results.
res.push(arr[i]);
}
}
}
// Otherwise, if the star is the last character
else if(starIndex === str.length - 1) {
// Get the string without the star.
str = str.substr(0, str.length - 1);
for(var i = 0; i < arr.length; i++){
// Check indexOf function
if(!arr[i].indexOf) continue;
// Check if the string is at the beginning of each item
if(arr[i].indexOf(str) === 0) {
// If it is, add the item to the results.
res.push(arr[i]);
}
}
}
// In any other case...
else {
for(var i = 0; i < arr.length; i++){
// Check indexOf function
if(!arr[i].indexOf) continue;
// Check if the string is anywhere in each item
if(arr[i].indexOf(str) !== -1) {
// If it is, add the item to the results
res.push(arr[i]);
}
}
}
// Return the results as a new array.
return res;
}
var birds = ['bird1','somebird','bird5','bird-big','abird-song'];
var res = searchArray(birds, 'bird*');
// Results: bird1, bird5, bird-big
var res = searchArray(birds, '*bird');
// Results: somebird
var res = searchArray(birds, 'bird');
// Results: bird1, somebird, bird5, bird-big, abird-song
There is an long list of caveats to a method like this, and a long list of 'what ifs' that are not taken into account, some of which are mentioned in other answers. But for a simple use of star syntax this may be a good starting point.
You could use Javascript's substring method. For example:
var list = ["bird1", "bird2", "pig1"]
for (var i = 0; i < list.length; i++) {
if (list[i].substring(0,4) == "bird") {
console.log(list[i]);
}
}
Which outputs:
bird1
bird2
Basically, you're checking each item in the array to see if the first four letters are 'bird'. This does assume that 'bird' will always be at the front of the string.
So let's say your getting a pathname from a URL :
Let's say your at bird1?=letsfly - you could use this code to check the URL:
var listOfUrls = [
"bird1?=letsfly",
"bird",
"pigs?=dontfly",
]
for (var i = 0; i < list.length; i++) {
if (listOfUrls[i].substring(0,4) === 'bird') {
// do something
}
}
The above would match the first to URL's, but not the third (not the pig). You could easily swap out url.substring(0,4) with a regex, or even another javascript method like .contains()
Using the .contains() method might be a little more secure. You won't need to know which part of the URL 'bird' is at. For instance:
var url = 'www.example.com/bird?=fly'
if (url.contains('bird')) {
// this is true
// do something
}
You should use RegExp (they are awesome) an easy solution is:
if( /^bird/.test(animals[i]) ){
// a bird :D
}
I think you meant something like "*" (star) as a wildcard for example:
or in your example: "bird*" => everything that starts with bird
I had a similar problem and wrote a function with RegExp:
//Short code_x000D_
function matchRuleShort(str, rule) {_x000D_
var escapeRegex = (str) => str.replace(/([.*+?^=!:${}()|\[\]\/\\])/g, "\\$1");_x000D_
return new RegExp("^" + rule.split("*").map(escapeRegex).join(".*") + "$").test(str);_x000D_
}_x000D_
_x000D_
//Explanation code_x000D_
function matchRuleExpl(str, rule) {_x000D_
// for this solution to work on any string, no matter what characters it has_x000D_
var escapeRegex = (str) => str.replace(/([.*+?^=!:${}()|\[\]\/\\])/g, "\\$1");_x000D_
_x000D_
// "." => Find a single character, except newline or line terminator_x000D_
// ".*" => Matches any string that contains zero or more characters_x000D_
rule = rule.split("*").map(escapeRegex).join(".*");_x000D_
_x000D_
// "^" => Matches any string with the following at the beginning of it_x000D_
// "$" => Matches any string with that in front at the end of it_x000D_
rule = "^" + rule + "$"_x000D_
_x000D_
//Create a regular expression object for matching string_x000D_
var regex = new RegExp(rule);_x000D_
_x000D_
//Returns true if it finds a match, otherwise it returns false_x000D_
return regex.test(str);_x000D_
}_x000D_
_x000D_
//Examples_x000D_
alert(_x000D_
"1. " + matchRuleShort("bird123", "bird*") + "\n" +_x000D_
"2. " + matchRuleShort("123bird", "*bird") + "\n" +_x000D_
"3. " + matchRuleShort("123bird123", "*bird*") + "\n" +_x000D_
"4. " + matchRuleShort("bird123bird", "bird*bird") + "\n" +_x000D_
"5. " + matchRuleShort("123bird123bird123", "*bird*bird*") + "\n" +_x000D_
"6. " + matchRuleShort("s[pe]c 3 re$ex 6 cha^rs", "s[pe]c*re$ex*cha^rs") + "\n" +_x000D_
"7. " + matchRuleShort("should not match", "should noo*oot match") + "\n"_x000D_
);If you want to read more about the used functions:
I used the answer by @Spenhouet and added more "replacements"-possibilities than "*". For example "?". Just add your needs to the dict in replaceHelper.
/**
* @param {string} str
* @param {string} rule
* checks match a string to a rule
* Rule allows * as zero to unlimited numbers and ? as zero to one character
* @returns {boolean}
*/
function matchRule(str, rule) {
const escapeRegex = (str) => str.replace(/([.*+?^=!:${}()|\[\]\/\\])/g, "\\$1");
return new RegExp("^" + replaceHelper(rule, {"*": "\\d*", "?": ".?"}, escapeRegex) + "$").test(str);
}
function replaceHelper(input, replace_dict, last_map) {
if (Object.keys(replace_dict).length === 0) {
return last_map(input);
}
const split_by = Object.keys(replace_dict)[0];
const replace_with = replace_dict[split_by];
delete replace_dict[split_by];
return input.split(split_by).map((next_input) => replaceHelper(next_input, replace_dict, last_map)).join(replace_with);
}
Source: Stackoverflow.com