Comment puis-je vérifier une chaîne vide/indéfini/null en JavaScript

92

if (strValue) {     //do something } 

if (strValue === "") {     //... } 

82

function isEmpty(str) {     return (!str || str.length === 0 ); } 

function isBlank(str) {     return (!str || /^\s*$/.test(str)); } 

String.prototype.isEmpty = function() {     // This doesn't work the same way as the isEmpty function used      // in the first example, it will return true for strings containing only whitespace     return (this.length === 0 || !this.trim()); }; console.log("example".isEmpty()); 

76

if (!!str) {     // Some code here } 

if (Boolean(str)) {     // Code here } 

68

if (!str.length) { ... 

52

if(str.replace(/\s/g,"") == ""){ }