CODEWITHSUNDEEP
javascript
Skizit
Skizit

Reputation: 44842

Convert Object to String

I've got an object returned from a field msg which is an object. I'm attempted to get the value from msg and convert it into a string so I can use .startswith(). I'm trying the following..

 var msgstring = msg.value
 if(msgstring.startsWith("string")){
    //Doing stuff!
 }

However, I get the following error...

Uncaught TypeError: Object string here has no method 'startsWith'

Where am I going wrong?

Upvotes: 3

Views: 6020

Answers (7)

Summved Jain
Summved Jain

Reputation: 890

As everybody has already mentioned that there is no startsWith function available with JS and we need to create a one for us. Below is the implementation for the same

if (typeof String.prototype.startsWith != 'function') {
  //Implementation to startsWith starts below
  String.prototype.startsWith = function (str){
    return this.indexOf(str) == 0;
  };
}

after doing this you can call the startsWith function directly with your string. this keyword will be the string on which you have called the function and str will be the string you are comparing with.

Upvotes: 0

The Mask
The Mask

Reputation: 17427

Try this:

var msgstring = msg.value;
 if(!msgstring.indexOf("string")){     
         //Doing stuff! 
 }

Upvotes: 0

tiagoboldt
tiagoboldt

Reputation: 2426

Exactly what you're reading, the string object (your variable msgstring) does not have a method called startsWith. Read more on using strings in here.

You probably want to do something like:

msgstring.substr(0, 6) == "string"

Upvotes: 0

ThiefMaster
ThiefMaster

Reputation: 318508

There is no startsWith() function in JavaScript. You need to write one yourself.

Upvotes: 0

Chris
Chris

Reputation: 7855

You are going wrong at assuming that there is a function called "startsWith". There is no such function in JavaScript.

Please have a look at this question:

How to check if a string "StartsWith" another string?

You will find there how you cann add this function to Javascript objects yourself.

Upvotes: 0

Shadow Wizard
Shadow Wizard

Reputation: 66389

The error is correct, JS has no native startsWith method of string object.

You can build it yourself extending the prototype, or use function:

function StartsWith(s1, s2) {
  return (s1.length >= s2.length && s1.substr(0, s2.length) == s2);
}

var msgstring = msg.value;
if(StartsWith(msgstring, "string") {
    //Doing stuff!
 }

Upvotes: 2

Sjoerd
Sjoerd

Reputation: 75599

Javascript has no startsWith method. You can use 

msgstring.indexOf('string') === 0

Upvotes: 16

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