JavaScript - Function for finding text within a string

Question

I have a function that I use to pass over a table field name and its value. Depending on the name of the field, it either returns the contents as a link or it does not.

// Given a field name, check to see if its in our output. If so, return the formatted link
function createLink(field, val) {
var output = {
 'ntid': 'https://web.internal/profile/' + val,
 'email': 'mailTo:' + val
};
var i, key, keys = Object.keys(output);
for ( i = 0; i < keys.length; ++i ) {
 key = keys[i];
 if(field.toLowerCase() == key){
 return '<a href="'+output[key]+'" target="_blank">'+val+'</a>';
 }
}
return val;
}

Usage:

createLink('email', '[email protected]') // returns <a href="mailto:[email protected]">[email protected]</a>

This also works for NTID. The issue I am having though is there are some field names that contain my values in the output such as Sup Email or Sup NTID and those are not transformed correctly.

Expected Result:

createLink('sup email', '[email protected]') // returns <a href="mailto:[email protected]">[email protected]</a>

The Question:

How can I tweak my function to see if my field exists in the output array at all, even if it's not an exact match?

• freginold: Best bet would be to use regex. Someone who's better with it than I am can probably provide a good pattern to use.

Answer 1

Change your function to

function createLink(field, val) {
 var output = {
 'ntid': 'https://web.internal/profile/' + val,
 'email': 'mailTo:' + val
 };
 var i, key, keys = Object.keys(output);
 for (i = 0; i < keys.length; ++i) {
 key = keys[i];
 if ((field.toLowerCase()).includes(key)) {
 return '<a href="' + output[key] + '" target="_blank">' + val + '</a>';
 }
 }
 return val;
}
console.log(createLink('sup email', '[email protected]') )

Notice the code if ((field.toLowerCase()).includes(key)) { This will check for your key substring in the string

Answer 2

What you're implementing is the Strategy Pattern. The Strategy Pattern relies on some form of behaviour-switching depending on the inputs to the method. In your case, that switching is based on the first argument.

What you don't want to do is what your questions asks how to do. You don't want to assume every field name in your application which contains "email" or some other string is guaranteed to be an email address, handled by the same strategy.

Create a table of field names and strategies to use for the display of each of these fields; and use an "enum-ish" object as the definition of the strategies.

function create_link(field, val) {
 const strategy = create_link.Field_Strategies[field];
 if (typeof strategy === 'undefined') {
 console.log("Using default strategy");
 return val;
 }
 console.log("Using " + strategy);
 switch (strategy) {
 case create_link.Strategies.EMAIL:
 return '<a href="mailto:' + val + '" target="_blank">' + val + '</a>';
 case create_link.Strategies.NTID:
 return '<a href="https://web.internal/profile/' +
 val + '" target="_blank">' + val + '</a>';
 case create_link.Strategies.SOME_FIELD:
 return '<a href="http://example.com/some/path/' +
 	encodeURIComponent(val) +
 	'" target="_blank">' + val + '</a>';
 }
}
create_link.Strategies = {
 EMAIL: "email strategy",
 NTID: "ntid strategy",
 SOME_FIELD: "somefield strategy"
};
create_link.Field_Strategies = {
 "Sup email": create_link.Strategies.EMAIL,
 "E-mail": create_link.Strategies.EMAIL,
 "Email": create_link.Strategies.EMAIL,
 "NTID": create_link.Strategies.NTID,
 "Foobar baz": create_link.Strategies.SOME_FIELD
};
console.log(create_link("foo","foofoofoo"));
console.log(create_link("Sup email","[email protected]"));
console.log(create_link("E-mail","[email protected]"));
console.log(create_link("Email","[email protected]"));
console.log(create_link("NTID","10983409509734"));
console.log(create_link("Foobar baz","Aleph null"));

Answer 3

You could use String.prototype.indexOf.

The indexOf() method returns the index within the calling String object of the first occurrence of the specified value...Returns -1 if the value is not found.

So your code would then look like:

// Given a field name, check to see if its in our output. If so, return the formatted link
function createLink(field, val) {
var output = {
 'ntid': 'https://web.internal/profile/' + val,
 'email': 'mailTo:' + val
};
var i, key, keys = Object.keys(output);
for ( i = 0; i < keys.length; ++i ) {
 key = keys[i];
 if(field.toLowerCase().indexOf(key) >= 0){ //CHANGE HERE
 return '<a href="'+output[key]+'" target="_blank">'+val+'</a>';
 }
}
return val;
}

• RBT: From review queue: May I request you to please add some more context around your answer. Code-only answers are difficult to understand. It will help the asker and future readers both if you can add more information in your post.