# Util
## F2.Util
## Methods
### `upperFirst([string=''])`
Converts the first character of string to upper case.
**Arguments**
* `[string='']` *(string)*: The string to convert.
**Returns**
*(string)*: Returns the converted string.
**Example**
```javascript
F2.Util.upperFirst('fred');
// => 'Fred'
F2.Util.upperFirst('FRED');
// => 'FRED
```
### `lowerFirst([string=''])`
Converts the first character of `string` to lower case.
**Arguments**
* `[string='']` *(string)*: The string to convert.
**Returns**
*(string)*: Returns the converted string.
**Example**
```javascript
F2.Util.lowerFirst('Fred');
// => 'fred'
F2.Util.lowerFirst('FRED');
// => 'fRED'
```
### `isString(value)`
Checks if `value` is classified as a `String` primitive or object.
\
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is a string, else `false`.
**Example**
```javascript
F2.Util.isString('abc');
// => true
F2.Util.isString(1);
// => false
```
### `isNumber(value)`
Checks if `value` is classified as a `Number` primitive or object.
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is a number, else `false`.
**Example**
```javascript
F2.Util.isNumber(3);
// => true
F2.Util.isNumber(Infinity);
// => true
F2.Util.isNumber('3');
// => false
```
### `isBoolean(value)`
Checks if `value` is classified as a boolean primitive or object.
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is a boolean, else `false`.
**Example**
```javascript
F2.Util.isBoolean(false);
// => true
F2.Util.isBoolean(null);
// => false
```
### `isFunction(value)`
Checks if `value` is classified as a `Function` object.
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is a function, else `false`.
**Example**
```javascript
F2.Util.isFunction(_);
// => true
```
### `isPlainObject(value)`
Checks if `value` is a plain object, that is, an object created by the `Object` constructor or one with a `[[Prototype]]` of `null`.
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is a plain object, else `false`.
**Example**
```javascript
function Foo() {
this.a = 1;
}
F2.Util.isPlainObject(new Foo);
// => false
F2.Util.isPlainObject([1, 2, 3]);
// => false
F2.Util.isPlainObject({ 'x': 0, 'y': 0 });
// => true
F2.Util.isPlainObject(Object.create(null));
// => true
```
### `isArray(value)`
Checks if `value` is classified as an `Array` object.
\
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is an array, else `false`.
**Example**
```javascript
F2.Util.isArray([1, 2, 3]);
// => true
F2.Util.isArray('abc');
// => false
```
### `isDate(value)`
Checks if `value` is classified as a `Date` object.
\
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is a date object, else `false`.
**Example**
```javascript
F2.Util.isDate(new Date);
// => true
F2.Util.isDate('Mon April 23 2012');
// => false
```
### `isNil(value)`
Checks if `value` is `null` or `undefined`.
\
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is nullish, else `false`.
**Example**
```javascript
F2.Util.isNil(null);
// => true
F2.Util.isNil(void 0);
// => true
F2.Util.isNil(NaN);
// => false
```
### `isObject(value)`
Checks if `value` is the [language type](http://www.ecma-international.org/ecma-262/7.0/#sec-ecmascript-language-types) of `Object`. *(e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)*
**Arguments**
* `value` *(\*)*: The value to check.
**Returns**
*(boolean)*: Returns `true` if `value` is an object, else `false`.
**Example**
```javascript
F2.Util.isObject({});
// => true
F2.Util.isObject([1, 2, 3]);
// => true
F2.Util.isObject(null);
// => false
```
### `mix(object, [sources])`
Assigns own enumerable string keyed properties of source objects to the destination object. Source objects are applied from left to right. Subsequent sources overwrite property assignments of previous sources.
**Arguments**
1. `object` *(Object)*: The destination object.
2. `[sources]` *(...Object)*: The source objects. Support for up to 3 objects
**Returns**
*(Object)*: Returns `object`.
**Example**
```javascript
const target = {
a: {
value: 1
}
};
const source = {
a: {
value: 2
},
b: 2
};
F2.Util.mix(target, source);
// => target will be { a: { value: 2 }, b2: 2 }
```
### `deepMix(object, [sources])`
This method is like `F2.Util.mix` except that it iterates over own source properties.
**Arguments**
1. `object` *(Object)*: The destination object.
2. `[sources]` *(...Object)*: The source objects.
**Returns**
*(Object)*: Returns `object`.
**Example**
```javascript
const target = {
a: {
type: 'a'
}
};
const source = {
a: {
value: 2
},
b: 2
};
F2.Util.mix(target, source);
// => target will be { a: { type: 'a', value: 2 }, b2: 2 }
```
### `indexOf(array, value)`
Gets the index at which the first occurrence of `value` is found in `array`.
**Arguments**
1. `array` *(Array)*: The array to inspect.
2. `value` *(\*)*: The value to search for.
**Returns**
*(number)*: Returns the index of the matched value, else `-1`.
**Example**
```javascript
F2.Util.indexOf([1, 2, 1, 2], 2);
// => 1
```
### `forEach(collection, [iteratee=_.identity])`
Iterates over elements of `collection` and invokes `iteratee` for each element. The iteratee is invoked with three arguments: *(value, index|key, collection)*. Iteratee functions may exit iteration early by explicitly returning `false`.
**Arguments**
1. `collection` *(Array|Object)*: The collection to iterate over.
2. `[iteratee=_.identity]` *(Function)*: The function invoked per iteration.
**Returns**
*(\*)*: Returns `collection`.
**Example**
```javascript
F2.Util.each([1, 2], function(value) {
console.log(value);
});
// => Logs `1` then `2`.
F2.Util.each({ 'a': 1, 'b': 2 }, function(value, key) {
console.log(key);
});
// => Logs 'a' then 'b' (iteration order is not guaranteed).
F2.Util.each([1, 2, 3, 4, 5, 6], function(value) {
console.log(value);
if (value === 4) {
return false;
}
});
// => Logs `1`,`2`,`3`,`4`.
```
### `getPixelRatio()`
Get the current pixel ratio.
**Returns**
*(number)*: Returns the current pixel ratio.
### `getRelativePosition(point, canvas)`
Convert the position of the mouse to the relative coordinate of the canvas.
**Arguments**
1. `point` *(Object)*: the point need to convert.
2. `canvas` *(Canvas)*: the canvas instance of chart.
**Returns**
*(object)*: Returns the relative coordinate of the canvas.
**Example**
```javascript
const mousePoint = {
x: 10,
y:39
};
const canvas = chart.get('canvas');
const canvasPoint = F2.Util.getRelativePosition(mousePoint, canvas);
// => { x: , y: }
```
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