javaScript function - why my default argument fails?
Default parameters is assigned only if no value or undefined is passed
let defaultStyle = { one: 1, two: 2, three: 3 }
function styling(style = defaultStyle, ...ruleSetStock) {
return ruleSetStock.map(ruleSet => {
return style[ruleSet]
})
}
console.log(styling(undefined, "one", "two", "three"))What if i want to use default value on all sorts of
falsy values such as false, '', null?
You can't use default parameter for that but you can use ||
let style1 = { one: 1, two: 2, three: 3 }
function styling(style, ...ruleSetStock) {
style = style || style1
return ruleSetStock.map(ruleSet => {
return style[ruleSet]
})
}
console.log(styling(undefined, "one", "two", "three"))
console.log(styling(null, "one", "two", "three"))
console.log(styling('', "one", "two", "three"))
console.log(styling(0, "one", "two", "three"))Two things you need to update
- Passing default parameter either no value or undefined
- changing the style default variable into another name
please see the updated code
let defaultStyle = {
one: 1,
two: 2,
three: 3
}
function styling(style = defaultStyle, ...ruleSetStock) {
return ruleSetStock.map(ruleSet => {
console.log(ruleSet)
return style[ruleSet]
})
}
console.log(styling(undefined, "one", "two", "three"))you can write the above snippet in much more cleaner way using es6
see the below snippet
const defaultStyle = {
one: 1,
two: 2,
three: 3
}
const styling = (style = defaultStyle, ...ruleSetStock) => ruleSetStock.map(ruleSet => {
return style[ruleSet]
})
console.log(styling(undefined, "one", "two", "three"))