js如何把一个变量转换成数字类型

 

　　　　　let a = 'a'
        let b =  true 
        let c = NaN
        let d = null
        let e = undefined
        let f = {}
        let g = []
        let h = {name:'zs'}
        let i = ['a']
        let j = '1.03'
        let k = '1.03a'
        let l = 'b1.03a'

 

 // 判断是否NaN
        let isNaN = a => a!=a?true :false

// 把变量转换成数字，不能转换的，就转成NaN

 let toNumber = a =>  {

            if(isNaN(a)){

                return a * 1

            }else{

                if(typeof(a) === 'number'){

                    return parseFloat(a)

                }else{

                    if(typeof(a) === 'string'){

                        return parseFloat(a)

                    }else{

                        return a * 1

                    }

                }

            } 

        }

 // 或者

 

        let toNumber2 = a =>  {

            if(isNaN(a)){

                return a - 0

            }else{

                if(typeof(a) === 'number'){

                    return parseFloat(a)

                }else{

                    if(typeof(a) === 'string'){

                        return parseFloat(a)

                    }else{

                        return  a - 0

                    }

                }

            }

        }

 　　　　console.log(toNumber(a)); // NaN

        console.log(toNumber(b)); // 1 

        console.log(toNumber(c)); // NaN

        console.log(toNumber(d)); // 0

        console.log(toNumber(e)); // NaN

        console.log(toNumber(f)); // NaN

        console.log(toNumber(g)); // 0

        console.log(toNumber(h)); // NaN

        console.log(toNumber(i)); // NaN

        console.log(toNumber(j)); // 1.03

        console.log(toNumber(k)); // 1.03

        console.log(toNumber(l)); // NaN