Musiyano uripo pakati pezvisina basa uye zvisina kujekeswa muJavaScript

Refer

Chaiwo mashandisiro e null

Seimwe paramende yebasa, zvinoreva kuti paramende yekushanda haisi chinhu

            function myFn(obj) {
    if(null == obj) {
        // code
    }
}
        

Sezvo kuguma kwechinhu prototype cheni

            Object.getPrototypeOf(Object.prototype);
        

Kana uchisunungura izvo zvinoshanduka, govera null kune iyo inosiyana

            let o={
 code:'abc'
};
o = null;
        

Chaiwo mashandisiro eisina kujekeswa

Musiyano unoziviswa asi hauna kupihwa, kukosha kweshanduko hakuna kujekeswa

            let o;
console.log(o);    //undefined
        

Iyo paramende iyo basa rinofanira kupa haina kupihwa kana uchinge wafona, ipapo kukosha kweparamende iyo isina kupihwa haina kujekeswa

            function myFn(o) {
    console.log(o);
}
myFn();   //undefined
        

Zvivakwa zvisina chinhu, kukosha kwacho hakuna kujekeswa

            let o={
 code:'abc'
};
console.log(o.name);    //undefined
        

Kana basa rikasadzosa kukosha, rinodzoka risina kujekeswa nekutadza

            function myFn(obj) {
    obj = 'a';
}
console.log(myFn());    //undefined
        

Kufanana pakati pe null uye zvisina kujekeswa

Kunyepa pakashandurwa kuita boolean

            console.log(Boolean(null));  // false
console.log(Boolean(undefined)); // false
        

Musiyano uripo pakati pezvisina basa uye zvisina kujekeswa

Mhedzisiro yacho yakasiyana kana ichishandurwa kuita nhamba.Mhedzisiro yekutendeuka kusingabvumirwe ndeyekukosha kwenhamba ye0, uye mhedzisiro yekusanzwisisika kutendeuka ndiNaN.

            console.log(Number(null));  // 0
console.log(Number(undefined)); // NaN
        

Mhando mbiri idzi dzakasiyana, mhando yezvisina chinhu, uye mhando yeiyo isina kujekeswa haina kujekeswa.

            console.log(typeof null); //object
console.log(typeof undefined); //undefined
        

enzanisa zvisina basa uye zvisina kujekeswa

Kupatsanura pakati pezvisina maturo uye zvisina kujekeswa, kungobatana chete ndiko kunogona kushandiswa.

            console.log(Boolean(null == undefined));  // true
console.log(Boolean(null === undefined)); // false
        

kupfupikisa

Mushure mekuenzanisa kuri pamusoro, isu tinonzwisisa zvakajeka mhando mbiri idzi. Kazhinji patinotonga kana musiyano uine kukosha kwakakodzera kana uchinyora kodhi, isu hatidi kusiyanisa pakati pezviviri, ingoishandisa seBoolean mhando. Asi kana isu tichida kutonga kuti chivakwa chiripo, isu tinofanirwa kunyatso shandisa iyo mhando kutonga isina kujekeswa Chekupedzisira, kana tikapasa kukosha kwenhamba, tinofanirwa kutanga tapa mutongo, uye hatigone kukandirwa kwakanangana nerudzi rwehuwandu, zvikasadaro zvinokonzeresa kuti tiwane mhedzisiro isina kujairika, uye isina kujekeswa ichaverenga zvakananga mhedzisiro isiri iyo NaN.