# Deep Set
> Set a nested property value.
## Usage
```javascript
var deepSet = require( '@stdlib/utils/deep-set' );
```
#### deepSet( obj, path, value\[, options] )
Sets a nested property value.
```javascript
var obj = { 'a': { 'b': { 'c': 'd' } } };
var bool = deepSet( obj, 'a.b.c', 'beep' );
// returns true
console.log( obj );
// => { 'a': { 'b': { 'c': 'beep' } } }
```
If the function is able to deep set a nested property, the function returns `true`; otherwise, the function returns `false`.
```javascript
var obj = { 'a': { 'b': { 'c': 'd' } } };
var bool = deepSet( obj, 'a.b.c', 'woot' );
// returns true
bool = deepSet( obj, 'a.beep.c', 'boop' );
// returns false
bool = deepSet( null, 'a.beep.c', 'boop' );
// returns false
bool = deepSet( 'bap', 'a.beep.c', 'boop' );
// returns false
```
For `paths` including `arrays`, specify the numeric index.
```javascript
var arr = [
{ 'a': [ { 'x': 5 } ] },
{ 'a': [ { 'x': 10 } ] }
];
var bool = deepSet( arr, '1.a.0.x', 25 );
// returns true
console.log( arr );
/* =>
[
{ 'a': [ { 'x': 5 } ] },
{ 'a': [ { 'x': 25 } ] }
]
*/
```
The key `path` may be specified as either a delimited `string` or a key `array`.
```javascript
var obj = { 'a': { 'b': { 'c': 'd' } } };
var bool = deepSet( obj, [ 'a', 'b', 'c' ], 'beep' ); // obj => { 'a': { 'b': { 'c': 'beep' } } }
// returns true
```
If `value` is a `function`, the argument is treated as a `callback` and should return a value to set.
```javascript
function set( val ) {
var ch = val;
var i;
for ( i = 0; i < 4; i++ ) {
val += ch;
}
return val;
}
var obj = { 'a': { 'b': { 'c': 'd' } } };
var bool = deepSet( obj, 'a.b.c', set ); // obj => { 'a': { 'b': { 'c': 'ddddd' } } }
// returns true
```
The function accepts the following `options`:
- **sep**: key path separator. Default: `'.'`.
- **create**: `boolean` indicating whether to create a path if the key path does not already exist. Default: `false`.
By default, the function assumes `dot` separated key values. To specify an alternative separator, set the `sep` option.
```javascript
var obj = { 'a': { 'b': { 'c': 'd' } } };
var bool = deepSet( obj, 'a/b/c', 'beep', {
'sep': '/'
});
// returns true
console.log( obj );
// => { 'a': { 'b': { 'c': 'beep' } } }
```
To create a key path which does not already exist, set the `create` option to `true`.
```javascript
var obj = { 'a': { 'b': { 'c': 'd' } } };
var bool = deepSet( obj, 'a.e.c', 'boop', {
'create': true
});
// returns true
console.log( obj );
/* =>
{
'a': {
'b': {
'c': 'beep'
},
'e': {
'c': 'boop'
}
}
}
*/
```
#### deepSet.factory( path\[, options] )
Creates a reusable deep set function. The factory method ensures a `deepSet` function is configured identically by using the same set of provided `options`.
```javascript
var dset = deepSet.factory( 'a/b/c', {
'create': true,
'sep': '/'
});
```
#### dset( obj, value )
Sets a nested property value.
```javascript
var dset = deepSet.factory( 'a.b.c' );
var obj = { 'a': { 'b': { 'c': 'd' } } };
var bool = dset( obj, 'beep' );
// returns true
console.log( obj );
// => { 'a': { 'b': { 'c': 'beep' } } }
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var deepSet = require( '@stdlib/utils/deep-set' );
var data;
var bool;
var keys;
var i;
function set( val ) {
return val * 10.0;
}
data = new Array( 100 );
for ( i = 0; i < data.length; i++ ) {
data[ i ] = {
'x': Date.now(),
'y': [ randu(), randu(), i ]
};
}
keys = [ 0, 'y', 2 ];
for ( i = 0; i < data.length; i++ ) {
keys[ 0 ] = i;
bool = deepSet( data, keys, set );
if ( !bool ) {
console.error( 'Unable to deep set value.' );
}
}
console.log( data );
```