Concatenating string inside javascript object definition

Question

I'm trying to put together a regex router that includes an arbitrary number of slugs and key-values.

I'm doing this by creating an object of patterns and their respective modules and will then match the regex to the module.

But JavaScript throws an error when I use the "+" operator to concatenate strings inside of the object definition.

// URI PATTERNS
var SLUG ='\/[a-z|A-Z|0-9|-]+)([\/]{0,1})?';
var KEYS ='\/?(\?.*)?$/';

// ROUTES 
var routes = {

    '\/public\/images'  +   KEYS                : 'images', /* <-- ERROR: '+' Unexpected token */
    '\/public\/other'   +   SLUG    +   KEYS    : 'something-else',

};

Why is this error being thrown and how can I concatenate these values outside of storing them in separate variables?

Object must have a property name and a value assigned to it. You can access the value in a object by its property. That is what you are missing — Rajshekar Reddy
– Rajshekar Reddy, Commented Nov 17, 2016 at 2:32
the property names are supposed to be the concatenated strings and the values would be the modules (images, etc) — yevg
– yevg, Commented Nov 17, 2016 at 2:37
Oh ya .. I overlooked it. You just need to use the [ ] to add property values then . Like just have a routes plain object like routes= {} then you can do routes[ your concatenation logic] = 'images'; — Rajshekar Reddy
– Rajshekar Reddy, Commented Nov 17, 2016 at 2:40
ah! yes. perfect. I guess I was trying to do it all in the declaration. thank you! — yevg
– yevg, Commented Nov 17, 2016 at 2:45

Dan Wilson · Accepted Answer · 2016-11-17 02:35:30Z

2

// URI PATTERNS
var SLUG = '\/[a-z|A-Z|0-9|-]+)([\/]{0,1})?';
var KEYS = '\/?(\?.*)?$/';

// ROUTES 
var routes = {};

function addRoute(keyParts, value){
  routes[keyParts.join('')] = value;
}

addRoute(['\/public\/images', KEYS], 'images');
addRoute(['\/public\/other', SLUG, KEYS], 'something-else');

console.log(routes);

answered Nov 17, 2016 at 2:35

Dan Wilson

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Comments

HenryDev · Accepted Answer · 2016-11-17 03:50:46Z

1

How about this solution. Hope it helps!

var SLUG ='\/[a-z|A-Z|0-9|-]+)([\/]{0,1})?';
var KEYS ='\/?(\?.*)?$/';

function obj(){
    obj=new Object();
    this.add=function(key,value){
        obj[key]=value;
    }
    this.obj=obj
}

routes=new obj();
routes.add(['\/public\/images'+ KEYS], 'images');
routes.add(['\/public\/other' + SLUG + KEYS],'something-else');

console.log(routes.obj);

edited Nov 17, 2016 at 3:50

answered Nov 17, 2016 at 2:52

HenryDev

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1 Comment

user663031 Over a year ago

What is the reason for doing ""+key+""? Why are you creating a new object inside the constructor when you could just say this.add = function(key, value) { this[key] = value; }?

user663031 · Accepted Answer · 2016-11-17 03:46:02Z

0

Use computed property names:

var routes = {
  [`\/public\/images${KEYS}`]: 'images',

The above also uses ES6 template literals.

answered Nov 17, 2016 at 3:46

user663031

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