Itandukaniro riri hagati yubusa kandi ridasobanuwe muri JavaScript

Reba

Imikoreshereze isanzwe yubusa

Nibikorwa byimikorere, bivuze ko ibipimo byimikorere atari ikintu

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

Nka iherezo ryikintu prototype

            Object.getPrototypeOf(Object.prototype);
        

Mugihe urekura impinduka, tanga null kubihinduka

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

Imikoreshereze isanzwe idasobanuwe

Impinduka iratangazwa ariko ntabwo yashinzwe, agaciro ka variable ntigasobanuwe

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

Ibipimo imikorere igomba gutanga ntabwo itangwa mugihe uhamagaye, noneho agaciro ka parameter idatanzwe ntigasobanuwe

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

Ibiranga ikintu kitarimo, agaciro ntigasobanuwe

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

Iyo imikorere idasubije agaciro, iragaruka idasobanuwe neza

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

Ibisa hagati yubusa nibidasobanutse

Ikinyoma iyo gihinduwe muri boolean

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

Itandukaniro riri hagati yubusa kandi ridasobanutse

Ibisubizo biratandukanye iyo bihinduwe kumubare.Ibisubizo byubusa ni umubare wemewe wa 0, kandi ibisubizo byo guhinduka bidasobanutse ni NaN.

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

Ubwoko bubiri buratandukanye, ubwoko bwa null ni ikintu, kandi ubwoko bwibidasobanutse ntibusobanuwe.

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

gereranya null kandi idasobanuwe

Gutandukanya ubusa nubusobanuro, gusa guhuza bishobora gukoreshwa.Mu guhuza, bizagereranya rwose niba ubwoko bwombi bungana.

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

guteranya

Nyuma yo kugereranya hejuru, dufite gusobanukirwa neza ubu bwoko bubiri. Mubisanzwe iyo dusuzumye niba impinduka ifite agaciro kemewe mugihe twandika code, ntidukeneye gutandukanya byombi, gusa uyikoreshe nkubwoko bwa Boolean. Ariko mugihe dukeneye kumenya niba umutungo uhari, tugomba gukoresha ubwoko kugirango ducire urubanza rudasobanutse. Hanyuma, niba dutsinze agaciro k'umubare, tugomba kubanza guca urubanza, kandi ntidushobora gutabwa muburyo bwimibare, bitabaye ibyo null bizadutera kubona ibisubizo bidasanzwe, kandi bidasobanuwe neza bizahita bibara ibisubizo bitemewe NaN.